Search

This study presents a state-of-the-art risk evaluation approach, designed for spatiotemporal multivariate environmental dynamic wind-wave systems, being either measured or Monte Carlo (MC) numerically simulated over a representative time-lapse. The main objective of this study has been to benchmark/validate the effectiveness and accuracy of the Gaidai multivariate risk evaluation methodology, using the application to in situ raw windspeeds, along with correlated wave-heights measurements, delivered by North Pacific area of the National Oceanic and Atmospheric Administration (NOAA) ocean buoys. The current study outlines a novel risk evaluation methodology, suitable for environmental dynamic systems, that are either MC numerically modeled, or directly physically measured. The intercorrelations between the wind-wave environmental system's critical/key dimensions and components, along with the high dimensionality of complex environmental systems, are not easily addressed by contemporary classic reliability methods. The objective of this study is to apply a novel reliability/risk evaluation methodology to a combined windspeed and correlated wave-height raw data set, recorded by the NOAA buoys within the North Pacific area, to demonstrate the efficiency of the proposed methodology. By reliability/risk assessment in the current study authors primarily mean probability forecast of certain multivariate hazard event. It is well known that when combined, windspeeds along with correlated wave heights form nonlinear dynamic environmental systems, that are complex, multidimensional, nonstationary, and yet intercorrelated. Global warming is only one of several significant factors that have ongoing impact on ocean windspeeds along with correlated wave heights, and environmental system risk evaluation is essential for marine, naval, and offshore structures, operating within specific in situ offshore areas of interest subject to realistic in situ ocean/sea weather conditions. The main goal of this study had been to benchmark and validate novel multivariate risk analysis methodology, making it possible to extract essential information directly from in situ raw environmental measurements. The methodology presented in this study opens the possibility of efficiently yet accurately assessing global failure/damage and hazard risks for multivariate nonstationary nonlinear environmental sea/ocean wind-wave systems. [ABSTRACT FROM AUTHOR]

Marine heatwaves (MHWs) are warm sea surface temperature (SST) anomalies with substantial ecological and economic consequences. Observations of MHWs are based on relatively short instrumental records, which limit the ability to forecast these events on decadal and longer timescales. Paleoclimate reconstructions can extend the observational record and help to evaluate model performance under near future conditions, but paleo-MHW reconstructions have received little attention, primarily because marine sediments lack the temporal resolution to record short-lived events. Individual foraminifera analysis (IFA) of paleotemperature proxies presents an intriguing opportunity to reconstruct past MHW variability if strong relationships exist between SST distributions and MHW metrics. Here, we describe a method to test this idea by systematically evaluating relationships between MHW metrics and SST distributions that mimic IFA data using a 2000-member linear inverse model (LIM) ensemble. Our approach is adaptable and allows users to define MHWs based on multiple duration and intensity thresholds and to model seasonal biases in five different foraminifera species. It also allows uncertainty in MHW reconstructions to be calculated for a given number of IFA measurements. An example application of our method at 12 north Pacific locations suggests that the cumulative intensity of short-duration, lowintensity MHWs is the strongest target for reconstruction, but that the error on reconstructions will rely heavily on sedimentation rate and the number of foraminifera analyzed. This is evident when a robust transfer function is applied to new core-top oxygen isotope data from 37 individual Globigerina bulloides at a site with typical marine sedimentation rates. In this example application, paleo-MHW reconstructions have large uncertainties that hamper comparisons to observational data. However, additional tests demonstrate that our approach has considerable potential to reconstruct past MHW variability at high sedimentation rate sites where hundreds of foraminifera can be analyzed. [ABSTRACT FROM AUTHOR]

The objective functions adopted by earthquake early warning (EEW) location algorithms are inadequate for out-of-network earthquakes. As a result, the real-time locations of these earthquakes are often erroneous. The consequences of mislocating out-of-network earthquakes are that their magnitudes are miscalculated, and the loci of their shaking predictions map are shifted. Given that the largest earthquakes occur in subduction settings, improving real-time out-of-network earthquake location is of great importance. In this study, the Virtual Dynamically Assembled Array Algorithm (ViDA³) is introduced, which addresses the location issue of offshore and off-network earthquakes. The guiding principle underlying the new EEW location algorithm is that standard seismic networks may be viewed as a collection of medium-sized seismic arrays, with each array consisting of three or more network stations. The potential of array seismology for EEW against out-of-network earthquakes stems primarily from the slowness vector, which points at the direction of the epicentral region. Thus, this region may be constrained merely by intersecting two or more such vectors. In addition, the length of the slowness vector depends on the hypocentral distance and depth and is thus vital for addressing an acute problem in a subduction setting--discriminating between upper crust and deep slab earthquakes. Furthermore, when the slowness of the P phase is known, the slowness of the S phase is deduced, and the S-phase arrival is searched for using the shift-and-sum practice. What makes ViDA³ so attractive is that, in locations where a real-time network is already in place, these added values may be achieved without extra hardware or substantial budget requirements. We present the result of ViDA³ real-time operation on a shallow earthquake offshore Vancouver Island and the result of its replay on a deep slab earthquake in northern Chile. performance is further assessed using a dataset of seismograms from the Mendocino Triple Junction area. It is concluded that ViDA³ location scheme outperforms currently available EEW location algorithms for out-of-network earthquakes. [ABSTRACT FROM AUTHOR]

The continuous rise in atmospheric CO2 levels has led to persistent ocean acidification, which negatively impacts marine environments crucial for marine life and alters the chemical composition of seawater. This phenomenon carries significant implications for human society. Utilizing surface seawater pH data from the North Pacific spanning 1995 to 2019, this study investigates the overall and localized spatiotemporal variations in pH within the region, as well as the factors influencing these variations. Additionally, it conducts a quantitative analysis of the different influencing factors. The findings reveal a consistent downward trend in surface seawater pH in the North Pacific, decreasing from 8.073 to 8.029, with notable seasonal variations. The highest pH values are recorded in winter, followed by spring, with lower values in autumn and summer. Spatially, the pH values are higher in the northwest and lower in the southeast, with the most pronounced acidification occurring in the central and western regions, while other areas exhibit more uniform acidification levels. Spatial correlation analysis indicates that surface seawater pH in the North Pacific generally shows a negative correlation with sea surface temperature (SST), salinity (SSS), and chlorophyll-a concentration (chl a) and a positive correlation with dissolved oxygen (DO). Among these factors, SST exerts the greatest influence on seawater pH, followed by DO and SSS. The degree of acidification varies across different regions, and the dominant influencing factors differ accordingly. In the equatorial central region (A), the primary factors are chl a and SST; in the eastern regions of China and Japan (B) and the western region of Canada (C), DO and SSS are the main controlling factors. An interaction analysis of each pair of dominant factors using the geodetector shows that their respective contributions to regions A, B, and C are 70%, 90%, and 50%, respectively. Understanding the primary factors driving acidification in different regions can aid in comprehending the biological and environmental impacts of acidification in those areas and provide valuable insights for mitigating marine acidification. [ABSTRACT FROM AUTHOR]

The North Pacific sea surface salinity (SSS) decadal variability (NPSDV) and its potential forcing were evaluated from 25 coupled models of the Coupled Model Intercomparison Project phase 6 (CMIP6) considering the prospects for decadal climate predictions. The results indicated that the CMIP6 models generally reproduced the spatial patterns of NPSDV. The large standard deviation of the SSS anomaly over the strong current regions, such as the Kuroshio-Oyashio Extension (KOE), North Pacific Current (NPC), California Current System (CCS), and Alaskan Coastal Current (ACC), is reflected in the two leading modes of NPSDV: a dipole with out-of-phase loadings in the KOE-NPC versus CCS-ACC and a monopole with positive loading over the KOE-NPC. The order of modes is sensitive to individual models that exhibit discrepancies, especially in temporal phases and power spectra. An autoregressive model of order-1 was used to reconstruct the NPSDV with several forcing terms. The generally weaker influence of forcings in an autoregressive model of order-1 is partly related to the overestimated response time of NPSDV relative to forcings. Most NPSDV variances originate from the persistence of SSS anomalies, but the dominant forcing factors are diverse among models. The model diversity for the NPSDV simulation mainly arises from the influence of the tropical El Niño-Southern Oscillation through teleconnection on the North Pacific Oscillation or Aleutian Low with timescale dependence. Conversely, models that can reproduce the NPSDV well are not dependent on those with larger impacts from the North Pacific oceanic processes. [ABSTRACT FROM AUTHOR]

Pacific salmon (Oncorhynchus spp.) spend much of their life near the ocean surface where climatic and oceanographic conditions affect their habitat and survival. Despite decades of study, critical knowledge gaps persist regarding their ecology and distributions. Consequently, it has been difficult to assess how environmental conditions influence the high‐seas distribution and habitat use of these culturally and socioeconomically important fishes, presenting challenges to fisheries managers trying to evaluate how climate change and fishing activities may impact salmon populations. We used a recently compiled, comprehensive database of historical coastal and high‐seas salmon survey data (1953–2022) in the North Pacific to fit species distribution models that (1) characterize the marine spatial distribution of six species of Oncorhynchus, (2) evaluate species‐specific temperature preferences, and (3) investigate how species' temperature preferences influence distribution. Sea surface temperature, along with seasonal migrations associated with spawning and feeding, significantly affects the distribution of all species, where the warm limits of estimated preferred thermal ranges were more similar than the cold limits. Furthermore, the distributions of some species appear more responsive to temperature than others and recently observed warm conditions have likely impacted realized ranges. These models have expanded our understanding of salmon ocean distributions and thermal niches by providing a unique window into this often unobserved but important part of the life cycle. They also serve as a baseline for future investigations into the mechanisms influencing salmon spatial ecology, responses to climate change, and vulnerability to harvest across the North Pacific. [ABSTRACT FROM AUTHOR]

The sei whale (Balaenoptera borealis) is an important species among baleen whales in the North Pacific and plays a significant role in the ecosystem. Despite the importance of this species, information regarding its migration patterns and breeding locations remains limited. To enhance the understanding of the phenology of North Pacific sei whales, we deployed satellite-monitored tags on these whales in the western and central North Pacific from 2017 to 2023. We fitted 55 sei whale tracks to a state-space model to describe the whales' seasonal movements at feeding grounds and their migratory behavior. The whales typically leave their feeding grounds between November and December, with migration pathways extending from off Japan to the west of the Hawaiian Islands. These southward transits converge in the waters of the Marshall Islands and north of Micronesia between 20° N and 7° N, which appear to be breeding grounds. After a brief stay at these breeding grounds, the whales migrate northward from January to February, reaching their feeding grounds around 30°N by March. To the best of our knowledge, this is the first study to present the phenology of feeding and breeding seasons and the migration pattern of North Pacific sei whales. [ABSTRACT FROM AUTHOR]

Age of cetaceans is an important data set for their conservation and management. Although the chronological age of a toothed whale has traditionally estimated from the number of annual tooth growth layer groups (GLGs), this method has potential difficulties such as errors due to the subjectivity of the age-readers and time-consuming sample processing, in addition to lethal tooth sampling in many cases. To overcome these difficulties through a non-lethal approach, considerable amount of efforts has been made in recent years to construct chronological age estimation models based on the correlation between chronological and biological age expressed as the frequency of DNA methylation at CpG (cytosine-phosphate-guanine) sites. The present study, by using next-generation sequencing on DNA extracted from the skin tissues of 30 individuals (15 males and 15 females), performed methylation analysis on multiple CpG sites in the three genes previously reported as age-linked in cetaceans (GRIA2, TET2, and CDKN2A) to construct an age estimation model for Risso's dolphins. Key aspects of this study are: (1) the chronological ages of Risso's dolphins of wild origins used in this study had been determined by the GLGs of teeth prior to this study, and (2) as Risso's dolphins are said to have a lifespan of 30 years, samples were collected from individuals aged 1-29 years, covering from young to old ages. Among the 11 CpG sites in GRIA2, 6 CpG sites in TET2, and 7 CpG sites in CDKN2A analyzed, the CpG sites in GRIA2 showed a statistically significant correlation with age, whereas those in TET2 and CDKN2A did not show such a strong correlation. Using multiple regression analysis on the CpG sites in the three genes, the best fitted model was expressed as follows: y=-0.7548 + 5.6164x(GRIA2_CpG3) +2.6187x(TET2_CpG6)-1.5907x(CDKN2A_CpG3) (R²=0.7062, residual mean=2.98, standard deviation=2.3). With the mean error of 2.98 years between the estimated and known chronological ages, the accuracy of this model was found to be comparable to or higher than that of previously reported age estimation models for cetaceans. This study demonstrated for the future that the age of wild Risso's dolphins can be estimated by using their skin samples collected with minimal invasiveness. [ABSTRACT FROM AUTHOR]

Abstract The sei whale (Balaenoptera borealis) is an important species among baleen whales in the North Pacific and plays a significant role in the ecosystem. Despite the importance of this species, information regarding its migration patterns and breeding locations remains limited. To enhance the understanding of the phenology of North Pacific sei whales, we deployed satellite-monitored tags on these whales in the western and central North Pacific from 2017 to 2023. We fitted 55 sei whale tracks to a state-space model to describe the whales’ seasonal movements at feeding grounds and their migratory behavior. The whales typically leave their feeding grounds between November and December, with migration pathways extending from off Japan to the west of the Hawaiian Islands. These southward transits converge in the waters of the Marshall Islands and north of Micronesia between 20° N and 7° N, which appear to be breeding grounds. After a brief stay at these breeding grounds, the whales migrate northward from January to February, reaching their feeding grounds around 30°N by March. To the best of our knowledge, this is the first study to present the phenology of feeding and breeding seasons and the migration pattern of North Pacific sei whales.

Founding populations of the first Americans likely occupied parts of Beringia during the Last Glacial Maximum (LGM). The timing, pathways, and modes of their southward transit remain unknown, but blockage of the interior route by North American ice sheets between ~26 and 14 cal kyr BP (ka) favors a coastal route during this period. Using models and paleoceanographic data from the North Pacific, we identify climatically favorable intervals when humans could have plausibly traversed the Cordilleran coastal corridor during the terminal Pleistocene. Model simulations suggest that northward coastal currents strengthened during the LGM and at times of enhanced freshwater input, making southward transit by boat more difficult. Repeated Cordilleran glacial-calving events would have further challenged coastal transit on land and at sea. Following these events, ice-free coastal areas opened and seasonal sea ice was present along the Alaskan margin until at least 15 ka. Given evidence for humans south of the ice sheets by 16 ka and possibly earlier, we posit that early people may have taken advantage of winter sea ice that connected islands and coastal refugia. Marine ice-edge habitats offer a rich food supply and traversing coastal sea ice could have mitigated the difficulty of traveling southward in watercraft or on land over glaciers. We identify 24.5 to 22 ka and 16.4 to 14.8 ka as environmentally favorable time periods for coastal migration, when climate conditions provided both winter sea ice and ice-free summer conditions that facilitated year-round marine resource diversity and multiple modes of mobility along the North Pacific coast.

The distribution of liverworts in the North Pacific is still poorly understood. Scapania umbrosa, which is rare in Asia, was first recorded during the study of the liverwort flora of the Commander Islands (the westernmost Aleutians). The results of the molecular genetic analysis not only confirmed that the specimen belonged to Scapania umbrosa but also demonstrated the genetic specificity of the discovered population in comparison with the European, Siberian, and Alaskan populations. The island population of Scapania umbrosa is likely a recently diverged isolate of the species. Previously reported data on the distribution of Scapania umbrosa in the Russian Far East from Kamchatka and Kunashir (VBGI Herbarium), as well as from Sakhalin and Southern Primorye (reported in GBIF), are based on misidentifications. Morphological descriptions, distinguishing characters, line drawings, and photographs of Scapania umbrosa based on the collected material are provided. [ABSTRACT FROM AUTHOR]

The North Pacific sea surface temperature (SST) has a profound climatic influence. The El Niño‐Southern Oscillation (ENSO) significantly impacts the North Pacific SST; however, the influence of the distinct phases of ENSO on SST predictability remains unclear. To overcome the model limitations, this study assessed SST predictability under diverse ENSO phases using reanalysis. The predictability limit of the North Pacific SST under La Niña (8.4 months) is longer than that under Neutral (5.9 months) and El Niño (5.5 months) conditions, which unveils asymmetry. This asymmetry mirrors contemporary multimodal prediction skills. Error growth dynamics reveal La Niña's robust signal strength with a slow error growth rate, in contrast to El Niño's weaker signal and faster error growth. There exhibits intermediate signal strength and elevated error growth in Neutral condition. Physically, predictability signal strength aligns with SST variability, whereas the error growth rate correlates with atmospheric‐ocean heating anomalies. La Niña, which induces positive heating anomalies, minimizes the impact of atmospheric noise, resulting in lower error growth. The result is beneficial for improving North Pacific SST predictions. Plain Language Summary: The North Pacific sea surface temperature (SST) significantly impacts global climate, particularly in East Asia and the United States. Accurate prediction of North Pacific SST, which is crucial for seasonal and interannual forecasting, remains a focal point in atmospheric and oceanic research. This study investigates how the El Niño‐Southern Oscillation (ENSO) influences SST predictability in the North Pacific during different phases (El Niño, La Niña, Neutral). Using reanalysis data, this research introduces the concept of predictability limit (PL), revealing an asymmetry in the PL response: La Niña extends the PL to 8.4 months, El Niño shortens it to 5.5 months, and Neutral falls in 5.9 months. This asymmetry aligns with the existing prediction skills. Examining the error growth dynamics, La Niña exhibits a robust SST signal with slower error growth, whereas El Niño displays a weaker signal with faster error growth. Neutral, meanwhile, shows a high signal strength but large error growth. This study sheds light on these differences in SST predictability and provides valuable insights for refining North Pacific SST predictions through model advancements. Key Points: El Niño‐Southern Oscillation phases asymmetrically impact North Pacific sea surface temperature (SST) predictability: El Niño (5.5 months), La Niña (8.4 months), Neutral (5.9 months)Error growth dynamics vary: La Niña displays strong signals with slow growth, El Niño exhibits weak signals and rapid growthA positive heating anomaly from La Niña reduces atmospheric noise impact, resulting in a smaller error growth rate of the North Pacific SST [ABSTRACT FROM AUTHOR]

Understanding the current status and recent development of the population genetics and connectivity of sea turtles is crucial for effective conservation management of the species. Five sea turtle species, green turtle (Chelonia mydas), loggerhead turtle (Caretta caretta), hawksbill turtle (Eretmochelys imbricata), olive ridley turtle (Lepidochelys olivacea) and leatherback turtle (Dermochelys coriacea), are recorded in the East Asia Region situated in the western side of the North Pacific Ocean. We compiled information from 35 published genetic studies on the five sea turtle species, with a focus on green turtle and loggerhead turtle, which are the most studied species (in 30 studies) in view of their commonness and occurrence of nesting populations. We provided an overview of the key methods and findings of these previous studies, addressing two main objectives on genetic structure of the rookeries and their differences compared to other populations, and connectivity of the rookeries and foraging aggregations. By identifying information gaps and conservation needs, we discussed future developments for sea turtle genetic studies and conservation implications in the region. [ABSTRACT FROM AUTHOR]

Evaluating the stratigraphy of the North Pacific is the first step towards understanding the role of this region in climate variability in the past. This region has been notoriously difficult to work in due to the presumed low sedimentation rates (<0.1 cm/kyr), which would likely be inadequate to capture glacial-interglacial cycles of the Late Pleistocene (∼500,000 years). These low sedimentation rates have been estimated from magnetostratigraphy and biostratigraphy, but those techniques are only minimally constrained during this geologically recent time period. Here, we reconstruct average sedimentation rates for the last 500 kyr across the deep (>3000 m) North Pacific using 230Th depth profiling, which is based on the exponential radioactive decay of 230Th and is one of only a few chronological tools applicable to sediment within this relatively calcium carbonate deficient region. Sedimentation rates are indeed low (<0.25 cm/kyr) within the subtropical gyre, especially between 20 and 30°N, but sedimentation rates greater than 0.5 cm/kyr are observed between 30 and 40°N, particularly west of 200°E. Sedimentation rates are higher underneath the Asian dust plume, and no water depth dependence is observed below 4000 m. Sedimentation rates from 230Th depth profiling generally agree with other methods, but they may be more representative of the average sedimentation rates for the last 500 kyr compared to other proxies that operate on much shorter (e.g., radiocarbon) or much longer (e.g., magnetostratigraphy) timescales. Overall, the efficacy of 230Th chronology is a promising tool for further investigation into the history of the North Pacific in the past. [ABSTRACT FROM AUTHOR]

This article seeks to complement efforts to summarize information on the exceptional natural significance of the Emperor Seamounts. The human history of the Emperor Seamounts is culturally diverse and spans thousands of years. This ranges from indigenous cultures to the period of European colonial exploration and expansion to the rise of the modern global economy and its impact on the area through the hunting of marine mammals, fishing, and the transportation of commodities across these remote waters on ships. Some of these vessels were wrecked or disappeared, and may rest on the seabed of the Emperor Seamounts. Understanding this human history is critical in approaching the assessment, ongoing study, public outreach and management of this remote region, which has been highlighted as one of the most important areas beyond national jurisdiction to protect globally. [ABSTRACT FROM AUTHOR]

The continuous rise in atmospheric CO2 levels has led to persistent ocean acidification, which negatively impacts marine environments crucial for marine life and alters the chemical composition of seawater. This phenomenon carries significant implications for human society. Utilizing surface seawater pH data from the North Pacific spanning 1995 to 2019, this study investigates the overall and localized spatiotemporal variations in pH within the region, as well as the factors influencing these variations. Additionally, it conducts a quantitative analysis of the different influencing factors. The findings reveal a consistent downward trend in surface seawater pH in the North Pacific, decreasing from 8.073 to 8.029, with notable seasonal variations. The highest pH values are recorded in winter, followed by spring, with lower values in autumn and summer. Spatially, the pH values are higher in the northwest and lower in the southeast, with the most pronounced acidification occurring in the central and western regions, while other areas exhibit more uniform acidification levels. Spatial correlation analysis indicates that surface seawater pH in the North Pacific generally shows a negative correlation with sea surface temperature (SST), salinity (SSS), and chlorophyll-a concentration (chl a) and a positive correlation with dissolved oxygen (DO). Among these factors, SST exerts the greatest influence on seawater pH, followed by DO and SSS. The degree of acidification varies across different regions, and the dominant influencing factors differ accordingly. In the equatorial central region (A), the primary factors are chl a and SST; in the eastern regions of China and Japan (B) and the western region of Canada (C), DO and SSS are the main controlling factors. An interaction analysis of each pair of dominant factors using the geodetector shows that their respective contributions to regions A, B, and C are 70%, 90%, and 50%, respectively. Understanding the primary factors driving acidification in different regions can aid in comprehending the biological and environmental impacts of acidification in those areas and provide valuable insights for mitigating marine acidification.

Recent research indicates that the midlatitude oceanic frontal zones are the key regions of ocean–atmosphere interaction. The thermal condition of midlatitude ocean in frontal zones can affect the atmosphere efficiently through both diabatic heating and transient eddy feedback. In this study, the wintertime SST variability in the subarctic frontal zone (SAFZ) of the North Pacific and the associated ocean–atmosphere interaction mechanism are examined based on observational and theoretical analyses. It is found that the SAFZ-related SST anomaly is characterized as a large-scale interannual mode that can persist during the whole winter, and that its evolution is accompanied with local ocean–atmosphere interaction processes. The initial anticyclonic surface wind anomaly associated with the weakened Aleutian Low forces a large-scale warm SST anomaly in midlatitude North Pacific by driving northward Ekman flow and downward heat flux. With the increase of SST anomaly, the air-sea heat flux exchange reverses, indicating that the ocean starts to heat the atmosphere. In addition to increasing the diabatic heating, the warm SST anomaly strengthens the SST gradient in the north part of SAFZ. The low-level atmospheric baroclinicity is adjusted to synchronize with the SAFZ correspondingly due to oceanic thermal influence, causing change of transient eddy activities. Though all the ocean-induced diabatic heating, transient eddy heating and transient eddy vorticity forcing are enhanced over SAFZ, the last physical process plays the most important role in shifting and maintaining the equivalent barotropic atmospheric circulation anomalies. Therefore, the ocean–atmosphere interaction provides a mechanism for the development and maintenance of SAFZ-related anomalies of the North Pacific ocean–atmosphere system throughout the winter. [ABSTRACT FROM AUTHOR]

The Shiretoko Peninsula, located at the southernmost point of the Sea of Okhotsk, was registered as a World Natural Heritage in 2005 in recognition of its rich biodiversity and an example of the interaction between marine and terrestrial ecosystems. However, there is insufficient information on its marine biota, which is an essential component of this ecosystem. This study was conducted from 2006 to 2019 to clarify the macroinvertebrate fauna along the shores of the Shiretoko Peninsula. A total of 299 species from 11 phyla were identified, including 118 mollusks, 107 crustaceans, 34 annelids, 24 echinoderms, and 16 species from other taxa, including two species recorded in Japan for the first time [Oregonia kurilensis (Decapoda: Brachyura) and Henricia alexeyi (Asteroidea: Echinasteridae)]. In addition, five species, including one new species of Isopoda, have been firstly reported from Japan based on the material collected by this project. Faunal similarity and biogeographical features differ between the Sea of Okhotsk side and the Nemuro Strait side of the peninsula, probably because of the effects of warm and cold currents, coastal topography, and drift ice pressure on the shore in winter. The macroinvertebrate fauna of the Shiretoko Peninsula is located at the boundary of different marine biogeographic provinces and is organized by environmental factors unique to the Sea of Okhotsk. Therefore, it is important to monitor the marine biota around the peninsula shores as these species act as bioindicators of environmental changes. [ABSTRACT FROM AUTHOR]

The fore-arc of the southern Cascadia subduction zone (CSZ), north of the Mendocino triple junction (MTJ), is home to a network of Quaternary-active crustal faults that accumulate strain due to the interaction of the North American, Juan de Fuca (Gorda), and Pacific plates. These faults, including the Little Salmon and Mad River fault (LSF and MRF) zones, are located near the most populated parts of California's north coast and show paleoseismic evidence for three slip events of several-meter scale in the past 1700 yr. However, the geodetic slip rates of these faults are poorly constrained. In this work, we analyze a new compilation of interseismic geodetic velocities from Global Navigation Satellite Systems, leveling, and tide gauge data near the MTJ to constrain present-day slip deficit rates on upper-plate faults and coupling on the megathrust. We construct Green's functions for interseismic slip deficit for discrete faults embedded in an elastic plate overlying a viscoelastic mantle. We then use a constrained least-squares inversion to determine best-fitting slip rates on the major faults and investigate slip rate trade-offs between faults. Results indicate that the LSF and MRF systems together accumulate 4-5 mm/yr of reverse-slip deficit, although their separate slip rates cannot be determined independently. Modeling of the horizontal and vertical velocities suggests that the southernmost CSZ is coupled interseismically to deeper than 25 km depth. We also find that 6-17 mm/yr of right-lateral slip deficit extends north of the MTJ and into the southern Cascadia fore-arc. These results reinforce the notion that both the southernmost Cascadia megathrust and the smaller fore-arc faults above it contribute to regional seismic hazard. [ABSTRACT FROM AUTHOR]

Changes in the path and intensity of jet streams have major impacts on regional weather and climate patterns. We investigated changes in the intensity, meridional position, and altitude of the North Pacific jet in different seasons during the period 1979–2020 using the European Centre for Medium-Range Weather Forecasts (ECMWF) fifth-generation reanalysis (ERA5) dataset. Our analysis indicates that the intensity and the meridional position of the North Pacific jet exhibit a pronounced seasonal cycle, with the most intense core of the jet in winter and its equatorward shift from 32.75 ∘ N in winter to around 40.75 ∘ N in summer. The jet also has a relatively large latitudinal spread in spring compared to the other seasons. The North Pacific jet has only weakened over the Yellow Sea in summer during the period 1979–2020. Maximum upper-tropospheric wind speeds have intensified over the Sea of Japan in winter in response to the poleward shift of the jet but weakened in spring due to the equatorward shift of the jet. Indeed, the jet has shifted poleward over the far western (125–140 ∘ E) and central (180 ∘ -150 ∘ W) North Pacific in winter, but the poleward shift of the jet is smaller over the far western North Pacific where the jet is stronger. This suggests that there might be a link between the speed of the North Pacific jet and the magnitude of its longitudinal poleward shifting variability. The jet has also shifted poleward over the central-eastern North Pacific (135–155 ∘ W) in summer, while changes in the altitude of the North Pacific jet have been insignificant during the period 1979–2020. The identified changes in the characteristics of the North Pacific jet have important implications for the understanding of weather patterns and the frequency of extreme events in the North Pacific and nearby regions. [ABSTRACT FROM AUTHOR]

Abstract The North Pacific sea surface temperature (SST) has a profound climatic influence. The El Niño‐Southern Oscillation (ENSO) significantly impacts the North Pacific SST; however, the influence of the distinct phases of ENSO on SST predictability remains unclear. To overcome the model limitations, this study assessed SST predictability under diverse ENSO phases using reanalysis. The predictability limit of the North Pacific SST under La Niña (8.4 months) is longer than that under Neutral (5.9 months) and El Niño (5.5 months) conditions, which unveils asymmetry. This asymmetry mirrors contemporary multimodal prediction skills. Error growth dynamics reveal La Niña's robust signal strength with a slow error growth rate, in contrast to El Niño's weaker signal and faster error growth. There exhibits intermediate signal strength and elevated error growth in Neutral condition. Physically, predictability signal strength aligns with SST variability, whereas the error growth rate correlates with atmospheric‐ocean heating anomalies. La Niña, which induces positive heating anomalies, minimizes the impact of atmospheric noise, resulting in lower error growth. The result is beneficial for improving North Pacific SST predictions.

Understanding the current status and recent development of the population genetics and connectivity of sea turtles is crucial for effective conservation management of the species. Five sea turtle species, green turtle (Chelonia mydas), loggerhead turtle (Caretta caretta), hawksbill turtle (Eretmochelys imbricata), olive ridley turtle (Lepidochelys olivacea) and leatherback turtle (Dermochelys coriacea), are recorded in the East Asia Region situated in the western side of the North Pacific Ocean. We compiled information from 35 published genetic studies on the five sea turtle species, with a focus on green turtle and loggerhead turtle, which are the most studied species (in 30 studies) in view of their commonness and occurrence of nesting populations. We provided an overview of the key methods and findings of these previous studies, addressing two main objectives on genetic structure of the rookeries and their differences compared to other populations, and connectivity of the rookeries and foraging aggregations. By identifying information gaps and conservation needs, we discussed future developments for sea turtle genetic studies and conservation implications in the region.

Introduction: Humpback whales belonging to the Central American (CA) Distinct Population Segment breed off the Pacific coast of Nicaragua. Knowledge on this endangered population and its conservation status is limited. Objective: The aim of this study is to provide the first description of the CA humpback whale song off Nicaragua, which helps further understanding on the population's dynamics. Methods: Acoustic recordings of songs were obtained during dedicated boat-based surveys at two locations on the Pacific coast of Nicaragua in 2018. Recordings were made from the boat using a portable system for a total of 23 hours and 56 minutes over 32 days from January to April 2018. A total of nine recordings of high enough quality for the song analysis were identified during this period from three different days at Padre Ramos (PR) (northern site) and four different days at San Juan del Sur (southern site). Song structure was described using standard humpback whale song elements, i.e. themes, phrases, and units. Results: A total of seven themes, seven phrases, and 19 unit types were identified. Three of the themes were common and frequently repeated in a song cycle while the others were less common in the repertoire and were recorded only during the middle of the season. Song theme order was variable, both within and across song sessions. Conclusions: This study provides the first song description of humpback whales along the Pacific coast of Nicaragua. Comparison of these songs with other datasets from the CA population and other breeding areas in the Northern Hemisphere could help understand the migratory patterns of these animals and the level of connectivity among populations since song can be socially learnt. Future data collection of humpback whale song recordings in Nicaragua is necessary to gain further understanding on the song structure variation within this population and the mechanisms of song transmission and dynamics across populations in the region. [ABSTRACT FROM AUTHOR]

Here, we examine extreme ocean winds associated with intense wintertime extratropical windstorms over the North Pacific. The study was mainly based on NASA Soil Moisture Active Passive (SMAP) L-band radiometer observations allowing the retrieval of ocean wind speeds up to 70 m/s regardless of precipitation intensity. Additionally, we assessed the ability of atmospheric reanalysis ERA5 and the Climate Forecast System Version 2 (CFSv2) to reproduce high-wind features within severe windstorms, particularly those associated with "explosive" cyclogenesis. The analysis identified 145 windstorm events with hurricane-force (HF) wind zones within the SMAP L-band radiometer swath from 2015 to 2023. These windstorms develop most frequently over two areas: southeast of Kamchatka and south of Alaska, spanning 40–47°N latitudes. Both reanalysis datasets significantly underestimated HF wind speeds compared to SMAP measurements, but CFSv2 tends to reproduce more-intense windstorms than ERA5. Among the notable new findings is that the SMAP data revealed two distinct groups in maximum wind speed distribution, indicating the existence of a separate class of severe windstorm events with a distinct mechanism for extreme wind formation related probably to a Shapiro–Keyser cyclogenesis and the presence of sting jet (SJ) feature. The study highlights the potential of SMAP measurements to study wind extremes and underscores the need for improvements in operational predictive models to better reproduce the formation of SJ windstorms. [ABSTRACT FROM AUTHOR]

The subseasonal variability of the low-cloud fraction (LCF) over the southeastern North Pacific (SENP) and northwestern North Pacific (NWNP) was studied using satellite observations and the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis. It is found that subseasonal variability of the LCF was closely related to variations in the estimated inversion strength (EIS), sea surface wind speed (SSW), sensible heat flux (SHF), sea surface temperature (SST), surface temperature advection (Tadv), relative humidity (RH), surface level pressure (SLP) and surface air temperature (SAT). An increase in the LCF over the SENP is associated with the development of an anomalous anticyclonic circulation, which is located on the west coast of America. The cold advection, together with the subsidence warming associated with the anticyclonic circulation, strengthens the temperature inversion, favoring the development of the LCF. In the NWNP, the maximum LCF anomaly was also correlated with the stable boundary layer. The southerly wind blows airflow over the Kuroshio Extension from the subtropics, which brings warm and moist air. When air flows to the colder sea surface, it is cooled and condensed by the intensified heat exchange. A lead-lag composite analysis indicates that the mechanisms are different between the SENP and the NWNP, possibly due to the different types of low-level clouds over these two regions. In the SENP, the trade cumulus dominates under a strong capping inversion over the subtropics, whereas fog and stratus often occur under a shallow capping inversion in the NWNP. The effects of atmospheric circulation are also discussed. [ABSTRACT FROM AUTHOR]

Geochemical analyses of trace elements in the ocean water column have suggested that pelagic clay‐rich sediments are a major source of various elements to bottom‐waters. However, corresponding high‐quality measurements of trace element concentrations in porewaters of pelagic clay‐rich sediments are scarce, making it difficult to evaluate the contributions from benthic processes to global oceanic cycles of trace elements. To bridge this gap, we analyzed porewater and bulk sediment concentrations of vanadium, chromium, cobalt, nickel, copper, arsenic, molybdenum, barium and uranium, as well as concentrations of the major oxidants nitrate, manganese, iron, and sulfate in the top 30 cm of cores collected along a transect from Hawaii to Alaska. The data show large increases in porewater concentrations of vanadium, manganese, cobalt, nickel, copper, and arsenic within the top cm of the sediment, consistent with the release of these elements from remineralized organic matter. The sediments are a sink for sulfate, uranium, and molybdenum, even though conditions within the sampled top 30 cm remain aerobic. Porewater chromium concentrations generally increase with depth due to release from sediment particles. Extrapolated to the global aerial extent of pelagic clay sediment, the benthic fluxes in mol yr−1 are Ba 3.9 ± 3.6 × 109, Mn 3.4 ± 3.5 × 108, Co 2.6 ± 1.3 × 107, Ni 9.6 ± 8.6 × 108, Cu 4.6 ± 2.4 × 109, Cr 1.7 ± 1.1 × 108, As 6.1 ± 7.0 × 108, V 6.0 ± 2.5 × 109. With the exception of vanadium, calculated fluxes across the sediment–water interface are consistent with the variability in bottom‐water concentrations and ocean residence time of the studied elements. Key Points: Porewater transition metal concentrations vary by up to an order of magnitude in aerobic pelagic clay sedimentsMost variability in porewater concentrations is observed in the top 5 cmCalculated benthic fluxes of most transition metals agree with estimated fluxes based on water column concentrations [ABSTRACT FROM AUTHOR]

Understanding how El Niño‐Southern Oscillation (ENSO) responds to natural variability is of key importance for future climate projections under a warming climate. However, there is no clear consensus on what drives ENSO's variability on centennial timescales. Here, we find that the epikarst in southeastern Alaska is effective at filtering ENSO and solar irradiance signals from the Aleutian Low regional climate, which are subsequently recorded in speleothem proxy data. By applying a correlation test, we find that ENSO was significantly influenced by solar irradiance over the past ∼3,500 years. This relationship dissolved after ∼1970 CE, with ENSO now being dominated by anthropogenic forcing. This implies a new ENSO mean state that will need to be incorporated into future climate projections. Plain Language Summary: Although El Niño‐Southern Oscillation (ENSO) is one of the most important climate phenomena globally, it is currently unknown how ENSO responds to natural variability on timescales over 100 years. Natural variability refers to periodic changes in climate due to either solar forcing, the circulation of the atmosphere and ocean, volcanic eruptions, and other factors, irrespective of human intervention. Here, we help solve this problem by studying deposits in caves (speleothems) from Alaska. The speleothems are excellent at capturing atmospheric conditions over the past 3,500 years, and show that solar forcing was significantly controlling ENSO variability. However, the speleothems also show that humans have altered this natural variability, with ENSO entering a new mean state after ∼1970 CE. Key Points: Speleothems from southeastern Alaska capture El Niño‐Southern Oscillation (ENSO) variability through a teleconnection with the Aleutian LowENSO variability was strongly influenced by solar forcing before ∼1970 CEENSO significantly changed properties at ∼1970 CE, likely due to anthropogenic forcing [ABSTRACT FROM AUTHOR]

Simple Summary: Subclass Ceriantharia encompasses marine anemone-like organisms with complete bilateral symmetry. In modern phylogenetic reconstructions, Ceriantharia is considered an ancient group that is sister to all other anthozoans. Only a handful of tube anemones have been reported from the Arctic, including widely distributed North Sea cerianthid Cerianthus lloydii Gosse, 1859, which has also been documented in temperate Atlantic and Pacific waters. The integrity of C. lloydii as a species has been questioned in the literature. To test this hypothesis, we performed a molecular study of C. lloydii from several geographically distant localities using 18S and COI genes. Our data combined with data from public databases show that C. lloydii forms a single genus-level group divided into three distinctive subclades: (1) Northern Europe, the Black and the Barents seas; (2) the Russian and Canadian Arctic and the Labrador Sea; and (3) published sequences of a species determined as Pachycerianthus borealis (Verrill, 1873) from Newfoundland. As all subclades of C. lloydii are only distantly related to the genus Cerianthus Delle Chiaje, 1841, we propose to resurrect the genus Synarachnactis Carlgren, 1924, and describe a new family to accommodate them. Our findings contribute to the understanding of the marine fauna evolution in the Arctic Basin and the Black Sea. Subclass Ceriantharia is a well-defined and probably ancient group of marine benthic organisms renowned for their bilateral symmetry, which is reflected in the arrangement of tentacles and mesenteries. Four species of Ceriantharia have been reported in the Arctic, including Cerianthus lloydii Gosse, 1859, also known from the Northern Atlantic and Northern Pacific. The integrity of this species was questioned in the literature, so we performed a molecular study of C. lloydii from several geographically distant locations using 18S and COI genes. The phylogenetic reconstructions show that specimens of C. lloydii form a single group with high support (>0.98), subdivided into distinctive clades: (1) specimens from Northern Europe, the Black and Barents seas, and (2) specimens from the White, Kara, Laptev, and Bering seas and also the Canadian Arctic and the Labrador Sea available via the BOLD database. There are several BOLD COI sequences of Pachycerianthus borealis (Verrill, 1873), which form a third clade of the C. lloydii group, sister to the European and Arctic clades. Based on low similarity (COI 86–87%) between C. lloydii and the type species of the genus Cerianthus Delle Chiaje, 1841—C. membranaceus (Gmelin, 1791), we propose a new status for the genus Synarachnactis Carlgren, 1924, and a new family Synarachnactidae to accommodate C. lloydii. [ABSTRACT FROM AUTHOR]

Abstract Understanding how El Niño‐Southern Oscillation (ENSO) responds to natural variability is of key importance for future climate projections under a warming climate. However, there is no clear consensus on what drives ENSO's variability on centennial timescales. Here, we find that the epikarst in southeastern Alaska is effective at filtering ENSO and solar irradiance signals from the Aleutian Low regional climate, which are subsequently recorded in speleothem proxy data. By applying a correlation test, we find that ENSO was significantly influenced by solar irradiance over the past ∼3,500 years. This relationship dissolved after ∼1970 CE, with ENSO now being dominated by anthropogenic forcing. This implies a new ENSO mean state that will need to be incorporated into future climate projections.

In this study, we obtained the first leading mode and principal component 1 (PC1) of North Pacific sea surface temperature (SST). The PC1‐related SST anomalies, located relatively north/south, are referred to as North/South PC1 events. Model outputs, observations, reanalysis datasets and sensitivity experiments show that during the North PC1 events, an enhanced Aleutian low occurs and is located relatively north, favoring anomalous southerlies over western North America. The anomalous southerlies induce a strong warming anomaly over North America via warm advection of the anomalous southerlies and temperature advection of the climatological westerlies over North America. However, the Aleutian low anomaly and corresponding southerly anomaly associated with South PC1 events shift southward, favoring weakened effects of South PC1 events on atmospheric circulations and surface temperatures over North America. The meridional position of PC1 events deserves to be considered in the studies of the PC1 and its related climate changes. Plain Language Summary: Understanding of surface temperature variations is important since it largely affects human and society. This paper categorizes the North Pacific sea surface temperature anomaly events, which are associated with the first leading mode of North Pacific sea surface temperature, into North and South events according to their meridional positions. Using model outputs, observations, reanalysis datasets and sensitivity experiments, we found that the surface temperature anomalies over North America during the North events are quite different from those during the South events. During the North events, an enhanced Aleutian low occurs over high‐latitude North Pacific. The enhanced Aleutian low tends to induce anomalous southerlies over western North America. The anomalous southerlies favor warming anomalies over North America via the warm advection of anomalous southerlies and temperature advection of climatological westerly. However, the Aleutian low anomaly and meridional wind anomaly during the South events shift southward, leading to weakened effects of the South events on atmospheric circulations and surface temperatures over North America. Key Points: North American warming anomaly occurs during North Pacific sea surface temperature anomaly events located northThe warming anomaly is related to an enhanced Aleutian low anomaly located north and climatological westerlyDuring the events located south, North American surface temperature responses are weak due to a southward‐shift Aleutian low anomaly [ABSTRACT FROM AUTHOR]

The Kuroshio Extension (KE) is known to undergo large decadal variations, especially after the 1976/77 climate regime shift. Due to strong ocean‐atmosphere interactions over the KE, the region may be a key region for basin‐scale Pacific decadal climate variability. Although baroclinic Rossby waves are suggested to influence the KE decadal variability, it remains unclear where and how decadal atmospheric forcing anomalies that induce the Rossby waves are generated. Using a linear Rossby wave model forced by reanalysis surface wind stress, the relative contribution of wind stress at each longitude is quantified for the first time. It is shown that the contribution is largest at 160°W, and 40% of the total variance in the decadal KE variability is explained by the wind forcing around 170°–150°W. Further analyses suggest that the atmospheric forcing anomalies are generated by the El Niño/Southern Oscillation Modoki through an atmospheric teleconnection after the regime shift. Plain Language Summary: The Kuroshio Extension (KE) is an intense eastward ocean flow in the western North Pacific formed after the Kuroshio separates from the Japanese coast. Satellite altimeter records and reanalysis products constrained by observational data have revealed that the KE strongly fluctuates with the decadal timescale between a stable and an unstable state, characterized by positive and negative sea surface height (SSH) anomalies to the south of the KE axis, respectively. A westward propagating oceanic wave with an SSH anomaly is considered as a primary cause of the phase reversal of the KE decadal variability. However, it has not been quantified to what extent wind forcing at each longitude contributes to the KE decadal variability through the ocean wave. In our study, we find that the largest contribution of wind forcing to the KE decadal variability is at 160°W, and 40% of the total variance in the KE variability is owing to wind forcing around 170°–150°W by simulation of westward propagating oceanic waves forced by reanalysis surface wind stress. Furthermore, it is suggested that the surface wind anomalies at 170°–150°W are remotely forced by a mode of climate variability in the tropical Pacific via an atmospheric bridge. Key Points: Wind forcing at 150°–170°W explains 40% of the total variance in Kuroshio Extension (KE) decadal variability via Rossby wavesThe dominant forcing at 150°–170°W is due to an atmospheric teleconnection of El Niño/Southern Oscillation (ENSO) ModokiThe statistically significant relation between KE decadal variability and ENSO Modoki is found only after the 1976/77 climate regime shift [ABSTRACT FROM AUTHOR]

Seabird species are increasingly threatened globally due to a range of anthropogenic impacts affecting at‐sea habitat. Characterizing at‐sea movement patterns and identifying foraging behaviour allows researchers to identify critical habitat but can be challenging for small diving species. The Ancient Murrelet Synthliboramphus antiquus is an alcid species of conservation concern in Canada. At‐sea distribution and movements of this species during the breeding season are currently poorly understood. We mounted GPS tracking devices on breeding Ancient Murrelets from two colonies along the southeastern coast of Haida Gwaii, one colony in 2018 and one in 2019, to collect movement data during foraging trips. We used hidden Markov models (HMMs) to identify three movement behaviour states from track characteristics, which we interpreted as transit, resting and foraging. Immersion data collected from the GPS tags allowed us to interpret the two slow‐moving states and to confidently identify foraging movement behaviour. From the 42 individuals tracked we found that foraging trips encompassed large areas of Hecate Strait, to the east of the colonies. Birds nesting on Ramsay Island in 2018 travelled on average 453 km in 4.3 days, up to a mean of 108 km from the colony. Birds breeding on George Island in 2019 took shorter trips, travelling on average 263 km in 3.0 days, and up to 81 km from the colony. In both years, birds spent approximately one‐third of their time in each behaviour state. Resting often took place throughout a whole night at sea; foraging occurred predominately during the day. Transit took place during the night, when birds were leaving or returning to the colony, or during the day, possibly indicating movement between prey patches. Our results can inform marine conservation of this vulnerable species by differentiating foraging from other at‐sea movement behaviours and is a first step to identifying critical foraging habitat. [ABSTRACT FROM AUTHOR]

Sea surface temperature (SST) anomalies in the Kuroshio Extension (KE) have been suggested to play a crucial role in decadal climate variability of the North Pacific affecting global climate and marine ecosystem variability. By analyzing the mixed layer heat budget, taking into account seasonality and mixed layer depth (MLD) variations, we here show for the first time that the KE SST front undergoes large decadal variations mainly owing to decadal modulations of the effective heat capacity affecting the SST sensitivity to surface heat fluxes during 1982–2015. More specifically, when the mixed layer becomes anomalously thick (shallow) to the south (north) of the front, it becomes less (more) sensitive to wintertime surface cooling. As a result, the SST front is strengthened, with positive (negative) SST anomalies to the south (north). A heat conservation model suggests that MLD anomalies are mainly due to thermocline depth anomalies. Plain Language Summary: Decadal climate variability of the North Pacific is known to affect global climate and marine ecosystem variability. The sea surface temperature (SST) front associated with the Kuroshio Extension (KE) in the northwestern Pacific is considered to play a key role in the turnabout of the North Pacific decadal climate variability. The fundamental question of how the strength of the SST front is modulated on the decadal timescale, however, has yet to be understood. Through quantitative analyses of oceanic and atmospheric data sets during 1982–2015, here we present for the first time that the KE SST front undergoes large decadal variations mainly owing to decadal modulation in thickness of the surface mixed layer that controls sensitivity of SST to surface heat exchange between the ocean and the atmosphere. Furthermore, a highly idealized model suggests that the anomalous mixed layer thickness is mainly due to anomalous oceanic stratification. Key Points: Generation mechanisms of decadal sea surface temperature (SST) anomalies associated with the Kuroshio Extension SST front is examinedA seasonally stratified mixed layer heat budget analysis with variable mixed layer depth (MLD) is conductedDecadal modulation in the MLD that controls sensitivity of SST to surface heat fluxes plays a key role during 1982–2015 [ABSTRACT FROM AUTHOR]

Diffuse attenuation coefficient of photosynthetically available radiation (PAR), KPAR, is a key product of ocean color remote sensing. Current ocean color algorithms generally detect only the average KPAR within one optical depth, K P A R R S . Due to the marked vertical variations of KPAR, knowledge of K P A R R S is insufficient to accurately evaluate the submarine light field. By using field in situ observations, a two-step approach, based on the development of an ocean color algorithm for K P A R R S and the relationships between K P A R R S and the average KPAR from the surface down to depth Z ( K ¯ P A R Z ), was developed to remotely estimate the vertical variations in K ¯ P A R Z in the North Pacific from the MODerate-resolution Imaging Spectrometer (MODIS) imagery. The root mean square difference of log( K ¯ P A R Z ) in depths within the euphotic zone was around ±0.059 (in unit of m−1 for K ¯ P A R Z ), which corresponded to a deviation of ±15% for the estimated K ¯ P A R Z and the penetration depths of PAR. Our study may provide a promising approach to detect the vertical variations of K ¯ P A R Z and underwater PAR distributions in the North Pacific Ocean. [ABSTRACT FROM AUTHOR]

Beginning from the mid-Cretaceous and in the Late Cretaceous, the landscape features of the North Pacific make it possible to divide this region into a number of territories called subregions. The earliest Cenophytic (with a significant number and diversity of angiosperms) late Albian–early Turonian Grebenka flora and its analogs are known only in three subregions of the North Pacific: Anadyr–Koryak, Northern Alaska, and Yukon–Koyukuk. In the middle of the Cretaceous, these subregions represented coastal plains and lowlands periodically flooded by the sea. Cenophytic floras populated the area of terrestrial volcanism of the Okhotsk–Chukotka subregion and the Asian continental interiors of the Verkhoyansk–Chukotka subregion later, in the Turonian–Coniacian. However, Mesophytic vegetation with the predominance of Early Cretaceous ferns and gymnosperms continued to exist there at least until the Coniacian. Consequently, the invasion of evolutionarily new Cenophytic vegetation into the continental interiors of Northeast Asia was gradual and extended over time. This should be taken into account when studying the Cretaceous nonmarine phytostratigraphy of the North Pacific region. [ABSTRACT FROM AUTHOR]

Selecting a reliable global climate model as the driving forcing in simulations with dynamic downscaling is critical for obtaining a reliable regional ocean climate. With respect to their accuracy in providing physical quantities and long-term trends, we quantify the performances of 17 models from the Coupled Model Inter-comparison Project Phase 6 (CMIP6) over the North Pacific (NP) and Northwest Pacific (NWP) oceans for 1979–2014. Based on normalized evaluation measures, each model's performance for a physical quantity is mainly quantified by the performance score (PS), which ranges from 0 to 100. Overall, the CMIP6 models reasonably reproduce the physical quantities of the driving variables and the warming ocean heat content and temperature trends. However, their performances significantly depend on the variables and region analyzed. The EC-Earth-Veg and CNRM-CM6-1 models show the best performances for the NP and NWP oceans, respectively, with the highest PS values of 85.89 and 76.97, respectively. The EC-Earth3 model series are less sensitive to the driving variables in the NP ocean, as reflected in their PS. The model performance is significantly dependent on the driving variables in the NWP ocean. Nevertheless, providing a better physical quantity does not correlate with a better performance for trend. However, MRI-ESM2-0 model shows a high performance for the physical quantity in the NWP ocean with warming trends similar to references, and it could thus be used as an appropriate driving forcing in dynamic downscaling of this ocean. This study provides objective information for studies involving dynamic downscaling of the NP and NWP oceans. [ABSTRACT FROM AUTHOR]

Odontocetes first appeared in the fossil record by the early Oligocene, and their early evolutionary history can provide clues as to how some of their unique adaptations, such as echolocation, evolved. Here, three new specimens from the early to late Oligocene Pysht Formation are described further increasing our understanding of the richness and diversity of early odontocetes, particularly for the North Pacific. Phylogenetic analysis shows that the new specimens are part of a more inclusive, redefined Simocetidae, which now includes Simocetus rayi, Olympicetus sp. 1, Olympicetus avitus, O. thalassodon sp. nov., and a large unnamed taxon (Simocetidae gen. et sp. A), all part of a North Pacific clade that represents one of the earliest diverging groups of odontocetes. Amongst these, Olympicetus thalassodon sp. nov. represents one of the best known simocetids, offering new information on the cranial and dental morphology of early odontocetes. Furthermore, the inclusion of CCNHM 1000, here considered to represent a neonate of Olympicetus sp., as part of the Simocetidae, suggests that members of this group may not have had the capability of ultrasonic hearing, at least during their early ontogenetic stages. Based on the new specimens, the dentition of simocetids is interpreted as being plesiomorphic, with a tooth count more akin to that of basilosaurids and early toothed mysticetes, while other features of the skull and hyoid suggest various forms of prey acquisition, including raptorial or combined feeding in Olympicetus spp., and suction feeding in Simocetus. Finally, body size estimates show that small to moderately large taxa are present in Simocetidae, with the largest taxon represented by Simocetidae gen. et sp. A with an estimated body length of 3 m, which places it as the largest known simocetid, and amongst the largest Oligocene odontocetes. The new specimens described here add to a growing list of Oligocene marine tetrapods from the North Pacific, further promoting faunistic comparisons across other contemporaneous and younger assemblages, that will allow for an improved understanding of the evolution of marine faunas in the region. [ABSTRACT FROM AUTHOR]

Several temperate marine taxa of the northern hemisphere follow a trans-Pacific biogeographic track with representatives on either side of the intervening boreal waters. Shelter-dwelling blenniiform fishes of the genus Neoclinus exhibit this trans-Pacific distribution pattern with three species in the eastern North Pacific and eight species in the western North Pacific. We reconstructed the phylogeny of the Neocliniini (Neoclinus and the monotypic Mccoskerichthys) using six genetic markers: four mitochondrial genes (COI, cytochrome b, 12S and 16S), and two nuclear genes (RAG-1, TMO-4C4). Ancestral state reconstruction and molecular clock dating were used to explore hypothetical ancestral distributions and area relationships, and to estimate divergent times within this group. The monophyly of the genus Neoclinus, and the reciprocal monophyly of the eastern Pacific and western Pacific lineages were supported. Available evidence, including the eastern Pacific and western Atlantic occurrence of a New World clade of blennioid fishes that includes this lineage, supports the origin of the Neocliniini in the eastern Pacific with a single divergence event to the west across the North Pacific by the ancestor of the western Pacific clade. Estimated divergence time of the eastern and western Pacific clades of Neoclinus was 24.14 million year ago, which falls during the Oligocene epoch. Estimated times of divergence in other trans-Pacific lineages of marine fishes vary widely, from recent Pleistocene events to as early as 34 mya.

Abstract Objectives The marine cyanobacterium Prochlorococcus is a critical part of warm ocean ecosystems and a model for studying microbial evolution and ecology. To expand the representation of this organism’s vast wild diversity in sequence collections, we performed a set of isolation efforts targeting low light-adapted Prochlorococcus. Three genomes resulting from this larger body of work are described here. Data description We present draft-quality Prochlorococcus genomes from enrichment cultures P1344, P1361, and P1363, sampled in the North Pacific. The genomes were built from Illumina paired reads assembled de novo. Supporting datasets of raw reads, assessments, and sequences from co-enriched heterotrophic marine bacteria are also provided. These three genomes represent members of the low light-adapted LLIV Prochlorococcus clade that are closely related, with 99.9% average nucleotide identity between pairs, yet vary in gene content. Expanding the powerful toolkit of Prochlorococcus genomes, these sequences provide an opportunity to study fine-scale variation and microevolutionary processes.

The relevance of the study is caused by the need to get knowledge of the fundamental scientific problem – the ferromanganese precipitation of the World Ocean. Marine ferromanganese deposits are records of sedimentation conditions in the past as well as promising mineral raw materials. Their formation is carried out under various processes, which are reflected in the bulk and isotopic composition of ferromanganese deposits. Currently, the least studied region of the Pacific Ocean is its northern segment. The main aim of the research is to study Sr and Nd isotopic composition of the ferromanganese crusts from the northern Pacific, formed under low detrital influx. Methods: litho-morphology; x-ray diffraction – determination of the mineral composition; mass spectrometric – determination of the chemical and isotopic composition. Results. Ferromanganese deposits of the guyots of the northern part of the Imperial Range (Detroit, Suzei, Hanzei) and the Amliya, Rat and Stailmate fracture zones, as well as the Vulkanolog Guyot (Magellan Seamounts), as a comparative material, were studied. Based on the mineralogical and geochemical bulk compositions, the studied ferromanganese deposits are classified as hydrogenetic ferromanganese crusts. The strontium isotopic composition of the studied samples is in the range from 0,70797 to 0,70919 (average 0,70885), with most of the samples concentrated at 0,709. At the same time, the content of strontium changes almost three times from 660 to 1700 ppm. The dependence of the isotopic composition on the concentration is not observed. The displacement of 87Sr/86Sr occurs towards volcanic rocks, which reflects the high amount of quartz-plagioclase admixture in the sample. The isotopic composition of neodymium, in terms of εNd, varies in the range from –3,5 to –3,0, which corresponds to the modern deep seawater of the North Pacific. An increase in εNd to –2,3 corresponds to a sample with the maximum terrigenous admixture. The minimum value of εNd (–4,4) was found in the bottom layer of the ferromanganese crust from the Hanzei Guyot. This value corresponds to the Miocene North Pacific Deep water. This is a reason to believe that in the Miocene the formation of the bulk composition of the North Pacific ferromanganese crusts was under North Atlantic Deep Waters entering through the Panama Gateway. The end of North Atlantic Deep Waters delivery to the Pacific was finished about five million years ago.

The North Pacific storm path has an important impact on the global climate. Studying the structure of regional precipitation along the North Pacific storm path will help better understand the role of the storm path in transporting water vapor and heat to the global atmosphere. Base on the GPM data and the fifth generation reanalysis data (ERA5) from European center for medium range weather forecasts (ECWMF), taking an extratropical cyclone event that occurred in the storm track area of the North Pacificfrom December 20 to 24 in 2014 as an example, we analyzed the characteristics of precipitation and cloud parameter structures for three precipitation segments brought by thiscyclone. The results show that the synoptic conditions of the three precipitation segments are similar, and their water vapor distributions are different from the north to the south, resulting in different distributions of water vapor flux divergence, which makes the precipitation intensities in the three segments different. The precipitation is concentrated in the southeast side of cyclone center. By comparing the relationship between precipitation intensity and water vapor content in extratropical cyclones, it is found that more precipitable water does not necessarily lead to greater precipitation intensity, but the column integrated water vapor content determines the upper limit of precipitation intensity. There are evident conversion layers of ice water in the vertical cross-sections of the reflectivity in the three precipitation segments, and the distribution of ice water conversion layers in each segment is different. According to the particle spectra of three precipitation segments obtained by dual frequency rain radar (DPR), the intensity distribution of effective particle radius of each segment is in good agreement with that of the reflectivity, while the distribution of particle number concentration is not consistent with the former two. The mechanism remains to be studied in future. The fusion of the GPM and ERA5 data can better reflect the synoptic conditions before and after the precipitation event on the North Pacific storm path, so as to explain its precipitation distribution, which can provide a reference for precipitation study in the areas of lacking ground observation data.

Piscine orthoreovirus genotype 1 (PRV-1) is an endemic virus to the Northeastern Pacific that infects both wild and farmed salmon. To better understand PRV-1 prevalence and transmission pathways in the region, we targeted out-migrating juvenile Pacific Salmon in the Strait of Georgia and Johnstone Strait in British Columbia, Canada, for PRV-1 molecular screening with an emphasis on Chinook (Oncorhynchus tshawytscha) and Coho (Oncorhynchus kisutch) salmon. A total of 4031 individuals were screened for PRV-1 and we identified an overall virus prevalence of 3.5% from 2011 to 2020. PRV-1 was absent in enhancement facilities and freshwater catchments and predominately found in the marine environment. The detection of PRV-1 varied greatly between species, year and stock of origin, but cumulatively identified that life history and migratory behaviors likely influenced viral prevalence. Specifically, Chinook salmon, which demonstrate long residence time in the Strait of Georgia relative to other species, had the highest PRV-1 prevalence in this study (7.4%). Varying stock composition and regional detection between year classes within the Strait of Georgia further indicated that the sources for Chinook infection were highly variable between years. These findings enhance our understanding for PRV-1 transmission in the region and more generally between/within salmon species. [ABSTRACT FROM AUTHOR]

The flux of dust deposition to the ocean and its impact on marine biological productivity are outstanding issues of the Earth's climate system. The North Pacific gyre (NPG) is the Earth's largest ecosystem and is important for marine nitrogen fixation, which is sensitive to Asian dust-regulated surface nutrient stoichiometry. Meanwhile, it is one of the least studied regions in the global ocean during the late Pleistocene, because of the extremely slow sediment accumulation and lack of biological material preservation. 232Th and 230Th concentrations recorded by hydrogenetic ferromanganese crusts in the deep NPG provide a novel and quantitative proxy of dust deposition and export productivity in this region. For this purpose, we have established an in situ U – Th isotope analytical technique on hydrogenetic ferromanganese crusts collected from the deep NPG. Iron, Mn, and Co of our samples have also been analyzed to constrain the impact of dust dissolution on the Fe geochemical cycle. Remarkably, variability of the 232Th-based dust flux over the last ∼900 ky exhibits a striking resemblance to grain-size records of the Chinese loess deposits and sea-level reconstructions but clearly decouples from the global temperature evolution. On orbital time scales, dust storms over the NPG are apparently sensitive to effects related to continental ice sheet sizes but decoupled from major global cooling during the early glaciation. While our 232Th data indicate a 2- to 3-fold variability of glacial – interglacial dust flux, scavenging of Fe, Mn, and Co in the deep NPG is much less variable through the late Pleistocene. We suggest that variable dust fluxes have a limited impact on the inventory of dissolved Fe in the deep waters of NPG, even though the scavenging of Fe has likely been regulated by glacial – interglacial paleoceanography. The paired 230Th-scavenging-based biological productivity tracks gyre sea surface temperature rather than dust flux during the last glacial cycle. We observe no correlation between dust flux and export productivity in the NPG, indicating that dust-derived Fe is not the productivity-limiting factor on orbital time scales in this region. Instead, these results imply that changes in gyre mixing and mode water formation might have led to increased supply of phosphorous and thus enhanced glacial biological carbon sequestration, with potentially stronger nitrogen fixation under higher eolian input. [ABSTRACT FROM AUTHOR]

Fishes of the genus Eleginus (Gadidae) are typical representatives of the ichthyofauna of the Northern Hemisphere; they play an important trophic role in the marine ecosystems of the Arctic and North Pacific and serve as targets of commercial and artisanal coastal fishing in many areas of the Russian North and Far East, as well as in areas of the coast of Alaska and northern Japan. The level of knowledge about the intraspecific organization of representatives of the genus Eleginus that is necessary for the rational exploitation of their stocks remains insufficient and their interspecific relationships have so far been analyzed using limited materials. This paper presents the first study of the interspecific relationships and intraspecific structure of navaga (E. nawaga) and saffron cod (E. gracilis) using a large-scale material (986 specimens in 29 samples from most of the species ranges) based on analysis of the polymorphism of mtDNA gene Cyt b. It is shown that they are independent, genetically differentiated species and their comparison with representatives of the genus Microgadus indicates that both species of the genus Eleginus might originate from a common ancestor close to M. proximus, while the divergence in the genus Microgadus occurred much earlier. Data on the haplotypic composition of saffron cod samples inhabiting areas from the Peter the Great Bay to Alaska waters and navaga samples inhabiting areas from the White Sea to the Ob Bay of the Kara Sea are given, which makes it possible to consider the phylogeographic history of both species and their intraspecific organization within the studied areas. Three groups can be distinguished for saffron cod: (1) Pacific–Japanese–Sakhalin group, (2) Chukchi–Bering seas group, and (3) intermediate group, which includes samples from the Sea of Okhotsk and waters of the northern Kurils. [ABSTRACT FROM AUTHOR]

Research has indicated that the meridional heat transport (MHT) in the North Pacific Ocean (NP) across 24°N increased in the 1980s and 1990s, resulting in different heat distributions: the ocean heat content (OHC) increased in the 1980s, while the net surface heat release was strengthened in the 1990s; however, the reasons for these differences remained unclear. The authors revisited the investigation of the heat budget in the NP mainly using hydrographic observations to understand why the heat distribution was different between these 2 decades and extend the analysis to the 2010s. The OHC in the upper 700 m north of 24°N and east of 137°E exhibited sharp increases around 1990 as well as in the 2010s, while it was nearly stable in between. The northward retreat of the subarctic gyre boundary coincided with the spin-up of the subtropical gyre in the late 1980s, thereby allowing warm anomaly from the subtropics to propagate northeastward. Meanwhile, the concurrent weakening of the wintertime westerlies resulted in the suppression of the surface heat loss in the western NP. In contrast, the southward shift of the subarctic front suppressed the OHC rise, despite the MHT increase in the late 1990s. In the 2010s, unprecedented warming occurred in the eastern NP. The MHT estimation based on hydrographic observations indicates that the net surface release must have been suppressed since the MHT did not increase; however, the latest atmospheric reanalysis datasets failed to reproduce this. [ABSTRACT FROM AUTHOR]

Abstract The Kuroshio Extension (KE) is known to undergo large decadal variations, especially after the 1976/77 climate regime shift. Due to strong ocean‐atmosphere interactions over the KE, the region may be a key region for basin‐scale Pacific decadal climate variability. Although baroclinic Rossby waves are suggested to influence the KE decadal variability, it remains unclear where and how decadal atmospheric forcing anomalies that induce the Rossby waves are generated. Using a linear Rossby wave model forced by reanalysis surface wind stress, the relative contribution of wind stress at each longitude is quantified for the first time. It is shown that the contribution is largest at 160°W, and 40% of the total variance in the decadal KE variability is explained by the wind forcing around 170°–150°W. Further analyses suggest that the atmospheric forcing anomalies are generated by the El Niño/Southern Oscillation Modoki through an atmospheric teleconnection after the regime shift.

Abstract In this study, we obtained the first leading mode and principal component 1 (PC1) of North Pacific sea surface temperature (SST). The PC1‐related SST anomalies, located relatively north/south, are referred to as North/South PC1 events. Model outputs, observations, reanalysis datasets and sensitivity experiments show that during the North PC1 events, an enhanced Aleutian low occurs and is located relatively north, favoring anomalous southerlies over western North America. The anomalous southerlies induce a strong warming anomaly over North America via warm advection of the anomalous southerlies and temperature advection of the climatological westerlies over North America. However, the Aleutian low anomaly and corresponding southerly anomaly associated with South PC1 events shift southward, favoring weakened effects of South PC1 events on atmospheric circulations and surface temperatures over North America. The meridional position of PC1 events deserves to be considered in the studies of the PC1 and its related climate changes.

Abstract Sea surface temperature (SST) anomalies in the Kuroshio Extension (KE) have been suggested to play a crucial role in decadal climate variability of the North Pacific affecting global climate and marine ecosystem variability. By analyzing the mixed layer heat budget, taking into account seasonality and mixed layer depth (MLD) variations, we here show for the first time that the KE SST front undergoes large decadal variations mainly owing to decadal modulations of the effective heat capacity affecting the SST sensitivity to surface heat fluxes during 1982–2015. More specifically, when the mixed layer becomes anomalously thick (shallow) to the south (north) of the front, it becomes less (more) sensitive to wintertime surface cooling. As a result, the SST front is strengthened, with positive (negative) SST anomalies to the south (north). A heat conservation model suggests that MLD anomalies are mainly due to thermocline depth anomalies.