Search

Detailed studies of wind-driven interbasin exchange in lakes, focusing on the underlying driving forces and how they are affected by stratification, are presently lacking. We therefore investigated how strati-fication modifies wind-induced exchange between the Petit Lac (PL) (depth 75 m) and Grand Lac (GL) (depth 309 m) basins of Lake Geneva in winter, using field observations, 3D hydrodynamic modeling and particle tracking. Early, weakly-stratified (December) and late, fully-mixed (March) winter condi-tions in the PL were compared for a typical, strong along-axis wind forcing. During early winter, two -layer exchange develops between the basins, with downwind surface outflow into the GL balanced by intense bottom inflow of deep, cold hypolimnetic GL water into the PL which is enhanced by baroclinic pressure gradients caused by upwelling in the GL. Furthermore, the transversal water-level setup gener-ates barotropic pressure gradients that balance Coriolis force acting on the outflow. This produces unidi-rectional along-wind epilimnion currents that strengthen interbasin exchange. In late winter, with the thermocline deeper than the PL bottom, upwelling in the GL does not reach the confluence and baroclin-icity plays no role, resulting in weaker exchange currents with a depth-veering structure in the upper lay-ers due to Coriolis force. In late winter, interbasin exchange decreases by 50 %, is more local, affects only waters near the confluence, and is more horizontal, with no deepwater upwelling from the GL. Our results suggest that prolonged winter stratification due to global warming will make wind-induced hypolimnetic interbasin-upwelling an increasingly important deepwater renewal process in large multi-depth basin lakes.(c) 2023 The Authors. Published by Elsevier B.V. on behalf of International Association for Great Lakes Research. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

The oceanic subsurface variability off East Africa in the tropical western Indian Ocean plays a crucial role in ocean dynamics and living resources as well as weather and climate variability. A regional ocean model is applied to understand the oceanic subsurface interannual variability off East Africa. The region with the highest sea surface temperature (SST) variability in the offshore region lies adjacent to strong subsurface temperature variations located between 30 and 130 m corresponding with strong variations in the thermocline depth. The weakest SST variations in the Tanzanian shelf waters lie over the subsurface waters with the smallest temperature variations in the upper 200 m with weak variations in the thermocline depth. Such signals are associated with induced forcings from the Indian Ocean Dipole (IOD) and El Niño-Southern Oscillation (ENSO) in both regions with different intensity and peaking times. The IOD-induced forcings are weaker, evolving in October and November-December in the region with the weakest and strongest SST variations, respectively. However, relatively stronger ENSO-induced forcings occur in both regions with stronger signals in the region with the strongest SST variations throughout the years except in August, and it peaks in January. The ENSO-induced forcings occur in January to May peaking in March and April in the region with the weakest SST. Consequently, anomalous Rossby waves as well as local Ekman downwelling and upwelling associated with both large-scale modes occur in the region leading to the subsurface temperature variations.

Lipid-biomarkers have been used to reconstruct environmental changes in lacustrine systems on a range of time scales. Lake sediments are excellent archives to apply these tools due to their rapid and amplified response to environmental pressures. For the past thirty years, the hypersaline lagoons of the Rio de Janeiro coastal plain have been studied as natural laboratories for the observation of the biogeochemical processes involved in modern dolomite precipitation. Here, we apply a multiproxy approach to characterize two depositional stages during the Holocene that may have triggered primary dolomite formation in these lagoonal environments. A first stage, with two sub-stages (1A − 6.1 to 4.2 kyr. BP; 1B − 4.2 to ∼3.6 kyr. BP) was deposited during the sea-level rise, with sediments containing an abundance of long-chain n-alkanes with 2H-depleted (δ2Hn-alk) signatures indicating riverine inputs of terrestrial organic carbon during prevailing wet conditions. A second stage (, Geochimica et Cosmochimica Acta, 337, ISSN:0016-7037, ISSN:1872-9533

CMIP6 model sea surface temperature (SST) seasonal extrema averaged over 1981–2010 are assessed against the World Ocean Atlas (WOA18) observational climatology. We propose a mask to identify and exclude regions of large differences between three commonly used climatologies (WOA18, WOCE-Argo Global Hydrographic climatology (WAGHC) and the Hadley Centre Sea Ice and Sea Surface Temperature data set (HadISST)). The biases in SST seasonal extrema are largely consistent with the annual mean SST biases. However, the amplitude and spatial pattern of SST bias vary seasonally in the 20 CMIP6 models assessed. Large seasonal variations in the SST bias occur in eastern boundary upwelling regions, polar regions, the North Pacific and the eastern equatorial Atlantic. These results demonstrate the importance of evaluating model performance not simply against annual mean properties. Models with greater vertical resolution in their ocean component typically demonstrate better representation of SST extrema, particularly seasonal maximum SST. No significant relationship of SST seasonal extrema with horizontal ocean model resolution is found.

Modeling the spatio-temporal distribution of Karenia brevis blooms in the Gulf of Mexico

Diatom, pollen, silicoflagellate, and biogenic opal analyses from a 155 cm-long gravity core from Pioneer Seamount, offshore Santa Cruz, California (PS1410-06 GC, latitude 37.3°N, longitude 123.4°W, water depth 2165 m) are compiled for the last ~11,300 years and compared with those of ODP 1019 and TN062-O550 from northern California. The relative abundance record of the subtropical diatom Fragilariopsis doliolus has similar bimodal Holocene patterns in all three cores, suggesting that sea surface temperatures (SST) were lower during the middle part of the Holocene than they were during the later and earlier parts. The relative abundance of coastal redwood (Sequoia sempervirens) pollen, a proxy for fog and coastal upwelling, displays stepwise increases in ODP 1019 and TN062-O550 between ~ 4000 and 3000 cal yr. BP, but its relative abundance in PS1410-06 GC increases gradually throughout the past 10,200 yr without any major steps. Similarly, biogenic silica (opal) displays stepwise increases at ~3600 and 2900 cal yr. BP in ODP 1019 and TN062-O550, respectively, whereas opal increases more gradually in PS1410-06 GC during the past 10,100 yr with relatively minor steps at ~3100 and ~2600 cal yr. BP. Together, coastal redwood and opal argue for a more gradual late Holocene increase in coastal upwelling along the coast of central California compared with that off northern California, where onshore-offshore gradients are more distinct.

Groundwater upwellings provide warmer, stable overwinter temperatures for developing salmon embryos, which may be particularly important in cold, braided, gravel-bed sub-Arctic rivers. We used a three-year time series of aerial counts and remote sensing to estimate the distribution of low and high aggregations of spawning fall chum salmon (Oncorhynchus keta), classify approximately 0.5 km long river segments by geomorphic channel type, and map thermal variability along a 25.4 km stretch of the Teedriinjik River, Alaska. We used a dynamic multistate occupancy model to estimate detectability, occupancy, and the dynamics of spawning aggregations among river segments. Detectability was higher for large (>150) relative to smaller aggregations. Unoccupied segments were likely to remain so from year to year; low abundance spawning segments were dynamic and rarely remained in that state for multiple years, while ∼20%–35% of high abundance segments remained stable, indicating the presence of high-quality spawning habitat. Spawning habitat use was associated with warmer water temperatures likely caused by groundwater upwellings. We identified spawning habitat characteristics and trends in usage by fall chum salmon, which will inform land management decisions and assist in evaluating impacts of shifting climate conditions and resource management on Arctic salmon populations.

Marine bivalve mollusc shells can offer valuable insights into past oceanographic variability and seasonality. Given its ecological and archaeological significance, Mytilus californianus (California mussel) presents the opportunity to examine seasonal and decadal changes recorded in its shell over centuries to millennia. While dark–light growth bands in M. californianus shells could be advantageous for reconstructing past environments, uncertainties remain regarding shell structure, environmental controls of dark–light band formation, and the amount of time represented by a dark–light pair. By analyzing a suite of M. californianus shells collected in 2002, 2003, 2019, and 2020 from Bodega Bay, California, we describe the mineralogical composition, establish relationships among growth band pattern, micro-environment, and collection season, and compare shell structure and growth band expression between the archival (2002–2003) and modern (2019–2020) shells. We identified three mineralogical layers in M. californianus: an outer prismatic calcite layer, a middle aragonite layer, and a secondary inner prismatic calcite layer, which makes M. californianus the only Mytilus species to precipitate a secondary calcite layer. Within the inner calcite layer, light bands are strongly correlated with winter collection months and could be used to reconstruct periods with moderate, stable temperatures and minimal upwelling. Additionally, modern shells have significantly thinner inner calcite layers and more poorly expressed growth bands than the archival shells, although we also show that growth band contrast is strongly influenced by micro–environment. Mytilus californianus from northern California is calcifying differently, and apparently more slowly, than it was 20 years ago.

The year-class success of small pelagic fish is strongly modulated by the growth and survival of early life stages. Determining how environments control growth is critical to understanding processes influencing annual production. We provide the first measurements of larval growth in Sardinella lemuru, the most abundant and exploited tropical sardine species in the Philippines. Growth rates of larvae were examined across a 2 yr period (2011-2012 and 2012-2013 spawning seasons) using otolith microstructure analysis. Transition to the juvenile stage occurred within 25 to 37 d. Mean growth rate of the 2011 year-class was significantly lower than the 2012 year-class despite significant intra-annual (batch) differences in growth trajectories. In both years, larvae that hatched and developed in the cooler yet prey-rich period in the middle of the spawning season (January) displayed the fastest growth, while those spawned early (September-October 2012) and late (February-March 2012) showed the slowest growth rates. Peak hatch-months (December 2011 and October 2012) were just prior to periods of upwelling, with mean prey concentrations of 0.24 ± 0.13 mg m-3 at 26.35 ± 2.56°C sea surface temperature (SST) and 0.23 ± 0.15 mg m-3 at 26.26 ± 1.79°C, respectively. The SST during upwelling was 0.01 to 1.23°C cooler accompanied by a 0.07 to 0.45 mg m-3 increase in prey concentration. In both years, differences in growth rate were strongly linked to oceanographic conditions. Moderate winds during a ‘neutral’ El Niño-Southern Oscillation year resulted in upwelling conditions favoring faster overall growth in larvae which was associated with stronger recruitment. In contrast, slower growth and weaker recruitment were associated with weak upwelling conditions in the 2011-2012 La Niña year. While temperature may be important, larval growth rates appear to be driven more by prey abundance.

Understanding the sources and biogeochemical processes influencing the dissolved iron (DFe) distribution is crucial because of its coupled role in C- and N-fixation in the oceans. Vertical depth profiles of DFe in the northwestern Indian Ocean along two meridional transects (∼65 °E and ∼57 °E) during spring and fall seasons are presented here under the GEOTRACES-INDIA initiative. The DFe in the surface waters exhibited both spatial and seasonal variabilities; N-S gradient with higher values in the north; and notably higher concentrations in the fall season. The photic zone-integrated DFe (57.5±13.4 µmol m-2) was double in the Arabian Sea compared to the subtropical Indian Ocean (31.81±7.63 µmol m-2) with a significant positive correlation with the photic zone integrated primary production. This suggests higher availability of DFe is responsible for high primary production in the Arabian Sea compared to the subtropical Indian Ocean. Lateral and vertical advection along with particle dissolution from the atmospheric dust fluxes and scavenging-adsorption processes could play a prominent role in controlling photic DFe concentrations in the Arabian Sea. The continental margin sources, redox chemistry, and remineralization are responsible for the observed high DFe concentration within the intense oxygen minimum zone. The in-situ remineralization ratios of Fe to C in the Arabian Sea are higher than any other region of the Indian Ocean. It could be due to the high uptake of Fe during primary production in the Arabian Sea, despite huge spatio-temporal variations in the abundance of phytoplankton communities. Our DFe data from the undersampled region over the Carlsberg Ridge suggests the presence of chronic/event plumes contributing to the DFe inventory in the western Arabian Sea region. We have approximated the geochemical budget of Fe in the top 100 m for open ocean waters of the Arabian Sea. These preliminary estimates suggest that lateral and vertical fluxes for DFe are prominent in the region compared to soluble atmospheric Fe dust fluxes and these sources are balanced by the biotic and abiotic removal processes in the region. Based on these estimated fluxes, the calculated residence time of DFe varies from ∼0.1 – 1 year in photic waters of the Arabian Sea. Our results highlight the intrusion of Fe-deficit Southern Ocean waters in the Arabian Sea and the upwelling of Fe-starved deep waters alongside the northwest of the Murray Ridge are likely responsible for Fe limitation in the region.

A suite of satellite-derived data and high-resolution ocean model outputs were used to study the response of the upper ocean to Hurricane Dorian (2019), which impacted the Bahamas and the eastern coast of the United States in August and September of 2019. We observe enhanced upwelling that in conjunction with surface cooling from precipitation led to an approximate 4 °C drop in sea surface temperature (SST) along and slightly ahead of Dorian's path. The upwelling also increased the local coastal chlorophyll-a levels. Soil Moisture Active Passive (SMAP) sea surface salinity (SSS) shows a clear eye and eye wall structure on September 4 (the day of peak intensity), which has never been seen due to the recency of the SMAP satellite's launch and the strength of Hurricane Dorian (2019). The initial forecast path of Hurricane Dorian was set to travel northward through central Florida; however, we can see from satellite observations that a high-pressure system in the north Atlantic redirects the path of the hurricane offshore. We show a clear upper ocean response to Hurricane Dorian using satellite observations and hope that this multiparameter approach can improve the current quantification of air-sea interactions during Category 5 conditions.

We investigate the impacts of one of the strongest recorded hurricanes to have hit the Florida Panhandle, Hurricane Michael (2018), on the upper ocean using a suite of satellite data, in situ profiles, and outputs from the HYbrid Coordinate Ocean Model (HYCOM). Strong, low-level cyclonic winds associated with the hurricane generated strong Ekman suction that propagated ahead of the hurricane and caused changes in the surface and subsurface ocean. Following the passage of Hurricane Michael, a 3 °C drop in sea surface temperature (SST) was accompanied with a 4-5 mg m⁻³ increase in chlorophyll-a concentration. In the subsurface, a ~15 m mixed layer deepening preceded upward displacements of the isotherms and cooling of the mixed layer. The impact of hurricane conditions on sea surface salinity (SSS) was localized and influenced by competing processes, with upwelling of salty subsurface water increasing SSS and enhanced precipitation decreasing SSS. During the peak of the hurricane, the impact of upwelling was greater than that of enhanced precipitation and, thus, SSS increased. Further away from the upwelling centers, hurricane-influenced precipitation, and river runoff freshened SSS.

Sea surface nitrate (SSN) is an important parameter to characterize physical and biogeochemical processes, particularly to quantify oceanic new primary production, yet its remote estimation from satellite has been difficult due to the complex relationships between environmental variables and SSN. In the central and southern sections of the California Current System (CSCCS), this challenge is attempted through modeling, validation, and extensive tests in different oceanic scenarios. Specifically, using extensive SSN datasets collected by many cruises spanning 40 years (1978-2018) and Moderate Resolution Imaging Spectroradiometer (MODIS) estimated sea surface temperature (SST) and chlorophyll-a (Chl), a stacking random forest (SRF) model of SSN has been developed and validated with a spatial resolution of ~4 km. The model showed an overall performance of root mean square difference (RMSD) = 0.83 μmol/kg, with coefficient of determination (R²) = 0.87, mean bias = -0.11 μmol/kg, and mean ratio = 1.15 for SSN ranging between 0.05 and 19.90 μmol/kg (N = 1034). Furthermore, tests of the model with its original parameterization for the upwelling period, oceanic period, and winter period all showed satisfactory performance with an overall RMSD of 1.95 μmol/kg. The sensitivity of the SRF model to uncertainties of MODIS SST and Chl was examined, with induced uncertainties of le 2.22 μmol/kg. The extensive evaluation and sensitivity tests indicated the robustness of the SRF model in estimating SSN in the study area of the CSCCS, and it could serve as a robust approach for other regions once sufficient in situ SSN data are available for model calibration.

IntroductionSubmarine canyons are incisive morphologies that play an important role in the exchange between shallow and deep waters. They interact with the general circulation and induce a specific circulation locally oriented by the morphology. The characteristics of the physical processes at play, the way they interact with each other and the influence of extreme events is still an open question as few observations are available. To answer this question and to improve the representation of submarine canyons in numerical models, it is key to understand the specific circulation patterns and their transitions in these specific environments.MethodsThis paper presents observations of currents, temperature and turbidity along the Cassidaigne canyon, northwestern Mediterranean Sea. Two oceanographic cruises carried out in 2017 and 2019 gathered data from the outer shelf and canyon head at 100-400 m depth to the base of the continental slope at 1900 m depth.Results and DiscussionThe circulation in the Cassidaigne area is subject to upwelling and downwelling-favorable winds, to the Northern Current and its associated mesoscale structures and is oriented by the local morphology. Upwellings occur both during stratified and non-stratified conditions. They are triggered by a wind forcing higher than 14 m s–1 and their consecutive relaxations are marked by a counter-current. Near the canyon head and on the shelf, the current orientation depends on the stratification, the wind, the bottom morphology and the general circulation. The mesoscale variability of the Northern Current can lead to its intrusion over the shelf leading to barotropic cross currents over the canyon. At 1700 m depth, a quasi-permanent residual up-canyon flow is observed in a narrow gorge area and can be extrapolated to the canyon body. Finally, turbidity currents were observed for the first time in connection with upwelling events, suggesting the key role of canyons’ internal hydrodynamics on shelf sedimentary processes.

Continental shelves are thought to be affected disproportionately by climate change and are a large contributor to global air–sea carbon dioxide (CO2) fluxes. It is often reported that low-latitude shelves tend to act as net sources of CO2, whereas mid- and high-latitude shelves act as net sinks. Here, we combine a high-resolution regional model with surface water time series and repeat transect observations from the Scotian Shelf, a mid-latitude region in the northwest North Atlantic, to determine what processes are driving the temporal and spatial variability of partial pressure of CO2 (pCO2) on a seasonal scale. In contrast to the global trend, the Scotian Shelf acts as a net source. Surface pCO2 undergoes a strong seasonal cycle with an amplitude of ∼ 200–250 µatm. These changes are associated with both a strong biological drawdown of dissolved inorganic carbon (DIC) in spring (corresponding to a decrease in pCO2 of 100–200 µatm) and pronounced effects of temperature, which ranges from 0 ∘C in the winter to near 20 ∘C in the summer, resulting in an increase in pCO2 of ∼ 200–250 µatm. Throughout the summer, events with low surface water pCO2 occur associated with coastal upwelling. This effect of upwelling on pCO2 is also in contrast to the general assumption that upwelling increases surface pCO2 by delivering DIC-enriched water to the surface. Aside from these localized events, pCO2 is relatively uniform across the shelf. Our model agrees with regional observations, reproduces seasonal patterns of pCO2, and simulates annual outgassing of CO2 from the ocean of +1.7±0.2 mol C m−2 yr−1 for the Scotian Shelf, net uptake of CO2 by the ocean of -0.5±0.2 mol C m−2 yr−1 for the Gulf of Maine, and uptake by the ocean of -1.3±0.3 mol C m−2 yr−1 for the Grand Banks.

In this contribution, we present the more or less consistent banding (mm to several cm) from Fe-rich to silica-rich chemical sediments associated with the venting that leads to the formation of banded sediments in several hydrothermal mineral systems, such as volcanogenic massive sulphides (VMS) and sedimentary exhalative (SEDEX) deposits. However, in this contribution we specifically refer to the banded sediments that are commonly known as Algoma-type iron formation (BIF). Algoma-type BIF does provide a somewhat unusual and poorly investigated case of chemical sediments banding. The banding of these chemical sediments in terms of Fe oxides and silica is related to their alternate dominance in the upwelling fluids in a variety of settings ranging from a sea floor spreading centre to continental rift-related settings. Equally important is the concept that Algoma-type BIF may well be associated with and a distal expression of sulphide-bearing mineral systems.

The open ocean region of southern Bay of Bengal (BoB) (~ 5° N–10° N; 87° E–97° E) is characterized as the region of low chlorophyll-a concentration (

The Indian Ocean presents two distinct climate regimes. The north Indian Ocean is dominated by the monsoons, whereas the seasonal reversal is less pronounced in the south. The prevailing wind pattern produces upwelling along different parts of the coast in both hemispheres during different times of the year. Additionally, dynamical processes and eddies either cause or enhance upwelling. This paper reviews the phenomena of upwelling along the coast of the Indian Ocean extending from the tip of South Africa to the southern tip of the west coast of Australia. Observed features, underlying mechanisms, and the impact of upwelling on the ecosystem are presented. In the Agulhas Current region, cyclonic eddies associated with Natal pulses drive slope upwelling and enhance chlorophyll concentrations along the continental margin. The Durban break-away eddy spun up by the Agulhas upwells cold nutrient-rich water. Additionally, topographically induced upwelling occurs along the inshore edges of the Agulhas Current. Wind-driven coastal upwelling occurs along the south coast of Africa and augments the dynamical upwelling in the Agulhas Current. Upwelling hotspots along the Mozambique coast are present in the northern and southern sectors of the channel and are ascribed to dynamical effects of ocean circulation in addition to wind forcing. Interaction of mesoscale eddies with the western boundary, dipole eddy pair interactions, and passage of cyclonic eddies cause upwelling. Upwelling along the southern coast of Madagascar is caused by the Ekman wind-driven mechanism and by eddy generation and is inhibited by the Southwest Madagascar Coastal Current. Seasonal upwelling along the East African coast is primarily driven by the northeast monsoon winds and enhanced by topographically induced shelf breaking and shear instability between the East African Coastal Current and the island chains. The Somali coast presents a strong case for the classical Ekman type of upwelling; such upwelling can be inhibited by the arrival of deeper thermocline signals generated in the offshore region by wind stress curl. Upwelling is nearly uniform along the coast of Arabia, caused by the alongshore component of the summer monsoon winds and modulated by the arrival of Rossby waves generated in the offshore region by cyclonic wind stress curl. Along the west coast of India, upwelling is driven by coastally trapped waves together with the alongshore component of the monsoon winds. Along the southern tip of India and Sri Lanka, the strong Ekman transport drives upwelling. Upwelling along the east coast of India is weak and occurs during summer, caused by alongshore winds. In addition, mesoscale eddies lead to upwelling, but the arrival of river water plumes inhibits upwelling along this coast. Southeasterly winds drive upwelling along the coast of Sumatra and Java during summer, with Kelvin wave propagation originating from the equatorial Indian Ocean affecting the magnitude and extent of the upwelling. Both El Niño–Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events cause large variability in upwelling here. Along the west coast of Australia, which is characterized by the anomalous Leeuwin Current, southerly winds can cause sporadic upwelling, which is prominent along the southwest, central, and Gascoyne coasts during summer. Open-ocean upwelling in the southern tropical Indian Ocean and within the Sri Lanka Dome is driven primarily by the wind stress curl but is also impacted by Rossby wave propagations. Upwelling is a key driver enhancing biological productivity in all sectors of the coast, as indicated by enhanced sea surface chlorophyll concentrations. Additional knowledge at varying levels has been gained through in situ observations and model simulations. In the Mozambique Channel, upwelling simulates new production and circulation redistributes the production generated by upwelling and mesoscale eddies, leading to observations of higher ecosystem impacts along the edges of eddies. Similarly, along the southern Madagascar coast, biological connectivity is influenced by the transport of phytoplankton from upwelling zones. Along the coast of Kenya, both productivity rates and zooplankton biomass are higher during the upwelling season. Along the Somali coast, accumulation of upwelled nutrients in the northern part of the coast leads to spatial heterogeneity in productivity. In contrast, productivity is more uniform along the coasts of Yemen and Oman. Upwelling along the west coast of India has several biogeochemical implications, including oxygen depletion, denitrification, and high production of CH4 and dimethyl sulfide. Although weak, wind-driven upwelling leads to significant enhancement of phytoplankton in the northwest Bay of Bengal during the summer monsoon. Along the Sumatra and Java coasts, upwelling affects the phytoplankton composition and assemblages. Dissimilarities in copepod assemblages occur during the upwelling periods along the west coast of Australia. Phytoplankton abundance characterizes inshore edges of the slope during upwelling season, and upwelling eddies are associated with krill abundance. The review identifies the northern coast of the Arabian Sea and eastern coasts of the Bay of Bengal as the least observed sectors. Additionally, sustained long-term observations with high temporal and spatial resolutions along with high-resolution modelling efforts are recommended for a deeper understanding of upwelling, its variability, and its impact on the ecosystem.

Volatile organic compounds (VOCs) affect oxidant loadings and secondary organic aerosol formation in the lower atmosphere. The marine environment is thought to be an important global source of biog...

The direction and magnitude of carbon dioxide fluxes between the atmosphere and the sea are regulated by the gradient in the partial pressure of carbon dioxide (pCO2) across the air–sea interface. Typically, observations of pCO2 at the sea surface are carried out by using research vessels and ships of opportunity, which usually do not resolve the diurnal cycle of pCO2 at a given location. This study evaluates the magnitude and driving processes of the diurnal cycle of pCO2 in a coastal region of the Baltic Sea. We present pCO2 data from July 2018 to June 2019 measured in the vicinity of the island of Utö at the outer edge of the Archipelago Sea, and quantify the relevant physical, biological, and chemical processes controlling pCO2. The highest monthly median of diurnal pCO2 variability (31 µatm) was observed in August and predominantly driven by biological processes. Biological fixation and mineralization of carbon led to sinusoidal diurnal pCO2 variations, with a maximum in the morning and a minimum in the afternoon. Compared with the biological carbon transformations, the impacts of air–sea fluxes and temperature changes on pCO2 were small, with their contributions to the monthly medians of diurnal pCO2 variability being up to 12 and 5 µatm, respectively. During upwelling events, short-term pCO2 variability (up to 500 µatm within a day) largely exceeded the usual diurnal cycle. If the net annual air–sea flux of carbon dioxide at our study site and for the sampled period is calculated based on a data subset that consists of only one regular measurement per day, the bias in the net exchange depends on the sampling time and can amount up to ±12 %. This finding highlights the importance of continuous surface pCO2 measurements at fixed locations for the assessment of the short-term variability of the carbonate system and the correct determination of air–sea CO2 fluxes.

The South China Sea (SCS) is the largest semi-enclosed marginal sea in the western Pacific. The alternation of East Asian monsoon causes a significant seasonal pattern of chlorophyll, primary productivity, and export flux of sinking particles. However, the source and sink of dissolved organic carbon (DOC) pools with different bioavailability are less studied. Here we evaluated the seasonal production of DOC in labile, semi-labile and refractory forms using a coupled physical-biogeochemical model. This study aims to understand the dynamics and budgets of organic matters in the SCS. Model results show that the production of labile, semi-labile and refractory DOC is highly correlated with the net primary productivity (NPP) which is higher in winter and lower in summer, reflecting a dependence of DOC on the NPP. The seasonal variation in Pearl River discharge dominates the DOC production in the northern coastal region. In the northeast, the Kuroshio intrusion associated frontal system is attributed to cause high winter production. The DOC production in the southwest is controlled by both winter mixing and summer upwelling. The production of refractory DOC with the least bioavailability favors carbon sequestration. Its annual mean production is 1.8±0.5 mg C m−2 d−1, equivalent to 26% of the export flux of particulate organic carbon at 1000 m.

Krill are an abundant and globally distributed forage taxon in marine ecosystems, including the California Current Ecosystem (CCE). The role of krill in trophodynamics depends on both abundance and size (biomass), but the impact of extreme climate events on krill body size is poorly understood. Using samples collected from 2011 to 2018, we tested the hypotheses that adult body length of three krill species (Euphausia pacifica, Thysanoessa spinifera, and Nematoscelis difficilis) declined during the 2014–2016 Northeast Pacific marine heatwave/El Niño event due to elevated seawater temperatures, reduced upwelling, and low primary productivity. Hierarchical mixed-effects modelling showed that mean length of adult E. pacifica and T. spinifera declined and N. difficilis length increased during 2015. These trends differed by sex and reverted to a pre-heatwave state in 2016. Temperature, upwelling, and food availability (chlorophyll-a content) did not explain decreased length in 2015, but environmental drivers of length varied regionally and by sex across all years. This study documents the impact of a major marine heatwave (MHW) on adult krill length in one of the world's major upwelling systems and indicates how pelagic ecosystems may respond to increasingly frequent MHWs.

The Ordovician shale (Wufeng Formation) in the Upper Yangtze Platform is now considered a successful development interval, independent of the Longmaxi Formation. However, accumulation mechanisms of organic matter (OM) within the Wufeng shale are rarely discussed and remain highly controversial. Petrological and geochemical characteristics were analyzed on 25 Wufeng samples from well X1 located in the Upper Yangtze Platform, and their implications for the OM accumulation mechanisms are further discussed. The Wufeng Formation is divided into three intervals based on graptolite biozones (named WF2, WF3, and WF4). Geochemical redox proxies (Mo, U, V, Ni, Cr, Co) suggest that WF2 and WF4 were deposited in oxic–suboxic conditions, whereas WF3 was deposited in suboxic–anoxic with episodes of euxinic conditions. Geochemical productivity proxies (Ba xs , P, Si xs ) indicate high paleoproductivity when WF2 and WF3 were deposited, which may have been controlled by upwelling as suggested by the high ratio of Cd/Mo. WF2 (averaged 1.42% TOC) is not as organic-rich because of poor preservation conditions and terrestrial dilution. High paleoproductivity and suitable preservation conditions were the controlling factors for the organic-rich WF3 interval (averaged 3.00% TOC). However, low paleoproductivity and poor preservation conditions caused low accumulation of OM in WF4 (averaged 0.82% TOC). OM accumulation within the Wufeng Formation reflects the interaction between the variations in redox conditions and paleoproductivity. The sedimentary environment during Wufeng deposition was mainly controlled by sea level, which, in turn, was controlled by global climate and global and regional tectonics.

The brown algal genus Lobophora (Dictyotales, Phaeophyceae) is an important ecological component of tropical marine systems. Although still scantily sampled, 35 species of Lobophora were discovered previously from the western Indian Ocean. This study updates previous diversity estimates by incorporating recent collections from Madagascar, Mozambique, and the Red Sea, considerably improving our knowledge of Lobophora diversity and biogeography in this region. Eight additional species are identified from the western Indian Ocean, raising the total number of Lobophora species to 43. Fifteen species are new to science and described herein. With ca. 40% of the global diversity, the western Indian Ocean is second only to the Central IndoPacific. Of the species identified to date, 29 appear to be restricted to the western Indian Ocean, three are shared with the Atlantic (four including L. lessepsiana introduced to the western Mediterranean Sea) and 12 have a wider distribution in the Indo-Pacific. The western Indian Ocean supports a high diversity with ca. 67% of its Lobophora restricted to this region, which is comparable to the Central Indo-Pacific (62%) and the Caribbean (61%). The presence of several putative endemic species in the western Indian Ocean islands and the Red Sea illustrates that these provinces played an important role in Lobophora species diversification within the western Indian Ocean by producing locally new species. The small number of species shared between the western Indo-Pacific and Atlantic indicates that this oceanic boundary - associated with the temperate Agulhas marine province, and the Benguela current and upwelling - acts as an effective dispersal barrier. info:eu-repo/semantics/publishedVersion

The thermocline-sea surface temperature (SST) feedback is the most important component of the Bjerknes feedback, which plays an important role in the development of the air-sea coupling modes of the Indian Ocean. The thermocline-SST feedback in the Indian Ocean has experienced significant decadal variations over the last 40 a. The feedback intensified in the late twentieth century and then weakened during the hiatus in global warming at the early twenty-first century. The thermoclidal variations of feedback are similar in these two regions, there are still differences in the underlying mechanisms. The decadal variations of feedback in the southeastern Indian Ocean are dominated by variations in the depth of the thermocline, which are modulated by equatorial zonal wind anomalies. Whereas the decadal variation of feedback in the southwestern Indian Ocean is mainly controlled by the intensityne-SST feedback is most prominent in the southeastern and southwestern Indian Ocean. Although the deca of upwelling and thermocline depth in winter and spring, respectively. The upwelling and thermocline depth are both affected by wind stress curl anomalies over the southeastern Indian Ocean, which excite anomalous Ekman pumping and influence the southwestern Indian Ocean through westward propagating Rossby waves.

Monthly sea surface temperature (SST) and chlorophyll-a (Chl-a) concentration during 1997–2018 in the Northern South China Sea (NSCS) were gap-filled using the Data INterpolating Empirical Orthogonal Functions (DINEOFs) approach. Good accuracy of the reconstructed data was verified based on an independent cross-validation data set. Significant spatial heterogeneities and seasonal variations were observed in the cloud-free SST and Chl-a data. An apparent decreasing trend in SST was found along the coast of Guangdong, east of Hainan Island, and in the Taiwan Strait with an average decreasing rate amounting to 0.01 °C per year. Increase in SST was observed in Beibu Gulf and the deep offshore region in the NSCS at an average rate as high as 0.009 °C per year. An increasing trend in Chl-a was detected in the northern Beibu Gulf, near the mouth of the Pearl River estuary, and around Shantou with an average rate of 0.005 mg $\cdot \text{m}^{-3}$ per year. EOF analysis of SST and Chl-a time series showed that the first three modes of both SST and Chl-a can explain most of their variances with accumulative contributions of 99.1% and 82.3%, respectively. The effects of surface net heat flux (NHF), Oceanic Nino Index (ONI), wind speed, and river flux on the first three modes of SST and Chl-a were quantitatively elucidated. Factors that affected the temporal and spatial variations of Chl-a and SST in the NSCS were qualitatively discussed, including El Nino-Southern Oscillation (ENSO), monsoon, upwelling, typhoon, internal waves, and Kuroshio intrusion.

The vegetation history and climate in southeastern Brazil, as well as the oceanic dynamics of the tropical Atlantic Ocean offshore, were reconstructed for the last 7.4 cal ka BP. This reconstruction was based on pollen, fern spores and dinoflagellate cysts identified in a marine core (CF10–04B). It was possible to verify the presence of an ombrophilous forest from 7.4 cal ka BP. Near the base of the PI zone low concentrations of pollen and fern spores are recorded, along with low frequencies of forest taxa and fern spores and an increase in pollen types of open vegetation, suggesting less humid climatic conditions than currently observed in the coastal regions of Southeastern Brazil. The assemblages of dinoflagellate cysts suggest a neritic zone with warm upper column temperature, high salinity and oligotrophic environment (evidenced by the presence of O. centrocarpum, Spiniferites spp. and L. machaerophorum). An increase in Tropical Waters (TW) and the approximation of the Brazilian Current (BC) in the middle shelf of southeastern Brazil in the mid-Holocene probably influenced the low accumulation of cysts, pollen grains, fern spores, and their associations. It is still possible to verify that at approximately 4.6 cal ka BP, an increase in the rainfall in the southeastern Brazilian region was probably the fundamental factor for the expansion of vegetation, mainly based on the considerable increases in hygrophytic and aquatic plants. The marked increase in the accumulation of dinoflagellate cysts, with the dominance of autotroph taxa (mainly O. centrocarpum, followed by Spiniferites spp), evidences the warmer waters of the BC and more intense surface upwelling of the South Atlantic Central Water (SACW).

Variations of chlorophyll-a (chl-a), sea surface temperature (SST) and net primary productivity (NPP) along with fish catch were studied along the coastal waters off Karnataka, west coast of India from January 2007 to December 2016. These variations are linked with the Indian Ocean Dipole and El Nino/Southern Oscillation—Nino3.4 SST index. NPP was estimated by using vertically generalized production model. Change in NPP values over the decade (2007–2016) was studied in context of global reports of decline in productivity over the period. It is very important to understand the pattern of NPP variability as well the interrelationship with SST over a long period to study its impact on distribution of the fishery resources. Trend showed that there is reduction in productivity after 2012 and this trend continued in subsequent years. During the study period, an increasing trend in SST is observed along the Karnataka coast. The present study shows that a strong El Nino event was seen in 2015, along with declined productivity in the coastal waters off Karnataka by ~ 24% and increase in SST by ~ 1% from the average of 10 years (2007–2016). Increased SST and low ocean productivity resulted in reduced fish catch with the decline of 6.7% in total fish catch along the Karnataka coast from 2014 to 2015. In 2016, 5.29 lakh tones of fish catch, was estimated resulting in 19.6%, increase compared to 2015. During southwest monsoon, sea surface height anomalies (SSHa) showed negative anomaly trend and increased Ekman pumping resulted in upwelling over the study area.

The initial interaction between material rising from the African Large Low Shear Velocity Province and the African lithosphere manifests as the Eocene continental large igneous province (LIP), centered on southern Ethiopia and northern Kenya. Here we present a geographically well-distributed geochemical dataset comprising the flood basalt lavas of the Eocene continental LIP to refine the regional volcano-stratigraphy into three distinct magmatic units: (1) the highly-alkaline small-volume Akobo Basalts (49.4–46.6 Ma), representing the initial phase of flood basalt volcanism derived from the melting of lithospheric-mantle metasomes, (2) the primitive and spatially restricted Amaro Basalts (45.2–39.58 Ma) representing the early main phase of flood basalt volcanism derived from the melting of the upwelling thermochemical anomaly, and (3) the spatially extensive Gamo-Makonnen magmatic unit (38-28 Ma) representing the mature main phase of flood basalt volcanism that has undergone significant processing within the lithosphere resulting in relatively homogeneous compositions. The focused intrusion of these main phase magmas over 10 m.y. preconditioned the African lithosphere for the localization of strain during subsequent episodes of lithospheric stretching. The focusing of strain into the region occupied by this continental LIP may have contributed to the initial extension in SW Ethiopia associated with the East African Rift.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5557626

In the present study, heat redistribution in the Tropical Indian Ocean (TIO) associated with the prolonged La Nina events during 1958–2017 is examined using reanalysis/observations. It is found that the prolonged La Nina forcing strengthened the east–west thermocline gradient in the equatorial Indian Ocean and propelled the eastward extension of thermocline ridge of the Indian Ocean (TRIO) from its climatological location of southwestern TIO. The cyclonic winds over the southeastern TIO and the associated upwelling Rossby waves are primarily driving the TRIO intensification and its eastward extension. Anomalous subsurface warming, thermocline deepening, and the associated increase in the upper ocean heat content and sea-level in the eastern equatorial Indian Ocean, southeastern TIO and Bay of Bengal (BoB) are found to be the characteristic features of the prolonged La Nina events. Cross equatorial Sverdrup transport near the eastern boundary during the prolonged La Nina events has increased the heat content of BoB and is found to be a pathway of Pacific water entering the north Indian Ocean.

Ocean dynamics in the equatorial Pacific drive tropical climate patterns that affect marine and terrestrial ecosystems worldwide. How this region will respond to global warming has profound implications for global climate, economic stability and ecosystem health. As a result, numerous studies have investigated equatorial Pacific dynamics during the Pliocene (5.3–2.6 million years ago) and late Miocene (around 6 million years ago) as an analogue for the future behaviour of the region under global warming1–12. Palaeoceanographic records from this time present an apparent paradox with proxy evidence of a reduced east–west sea surface temperature gradient along the equatorial Pacific1,3,7,8—indicative of reduced wind-driven upwelling—conflicting with evidence of enhanced biological productivity in the east Pacific13–15 that typically results from stronger upwelling. Here we reconcile these observations by providing new evidence for a radically different-from-modern circulation regime in the early Pliocene/late Miocene16 that results in older, more acidic and more nutrient-rich water reaching the equatorial Pacific. These results provide a mechanism for enhanced productivity in the early Pliocene/late Miocene east Pacific even in the presence of weaker wind-driven upwelling. Our findings shed new light on equatorial Pacific dynamics and help to constrain the potential changes they will undergo in the near future, given that the Earth is expected to reach Pliocene-like levels of warming in the next century. New proxy data for ocean pH and an ocean–atmosphere model show that a radically different ocean circulation led to decoupling of ocean productivity and upwelling in the equatorial Pacific Ocean 3–6 million years ago.

In this study, we diagnose the time variability and vertical structure of the high- and low-frequency motions on the Mississippi-Alabama Shelf as observed with a bottom-mounted ADCP (Acoustic Doppler Current Profiler) and CTD (Conductivity-Temperature-Depth). The mooring was deployed about 20 km offshore of Mobile Bay for a period from May 17 to August 23, 2018. At this latitude, the diurnal land and sea breeze has the same frequency as the local inertial frequency. Similar to the wind, the observed high-frequency baroclinic velocities (> 30 cm/s) have a broadband diurnal peak and more energy in the clockwise motions. About 60% of the variance in these motions is due to mode 1, which resembles a two-layer structure with surface and bottom velocities that are 180∘ out of phase. These are all characteristics of wind-driven motions that interact with the coastal wall. The month of June features the best conditions for energetic near-inertial motions: upwelling, consistent sea breeze, and a more continuous instead of a two-layer stratification. This causes near-inertial energy to be also projected on a baroclinic mode 2, featuring a subsurface maximum. This maximum may be attributed to the downward propagation of near-inertial internal wave energy. The observed alongshore low-frequency flows and the up- and downwelling are mostly driven by low-frequency winds. About 83% of the variance in the alongshore low-frequency flows is due to mode 1, which eigenfunction resembles a vertically sheared flow. We find that the amplitude of the near-inertial motions is modulated by the up- and downwelling. During downwelling, the near-inertial baroclinic kinetic energy is greatly reduced because of a reduction in stratification and weaker diurnal winds.

We present measurements of sunlit aurora during the launch of the Rocket Experiment for Neutral Upwelling 2 (RENU2) on the 13 December 2015, 07:34 UTC. The in situ auroral conditions coincide with those of sunlit aurora and were characterised by the 391.4 and 427.8 nm N2+ emissions. A correlation between several auroral wavelengths, as measured by a meridian-scanning photometer, was used to detect sunlit aurora and indirectly neutral upwelling. These results, based on ground data, agree well with the RENU2 measurements recorded during its pass through the sunlit polar cusp. Using in situ data from RENU2 and the solar photon flux, it was estimated that the sunlit aurora was a major part (≈40 %) of the observed 427.8 nm emission.

A subsurface oxygen minimum layer (OML) in intermediate water is identified and characterized in Rivers Inlet, a fjord on British Columbia’s central coast, using data from 1998 to 2018. The OML was observed in most years from May to September and was most persistent at the middle and head of the fjord. The Rivers Inlet OML develops in three stages: (i) in early spring, the cessation of winter storms from downwelling-favourable winds stops the ventilation of the water column; (ii) throughout spring and summer, the remineralization of organic matter, likely primarily phytoplankton, consumes oxygen in the intermediate waters; (iii) in late spring, deep-water renewal by oxygenated offshore water forms the base of the OML inside the inlet. The strength and persistence of the OML vary interannually, mainly due to variability in hemispheric-scale winds and primary production. In some years, the OML was hypoxic, which could influence the local marine ecosystem. Changes to downwelling, upwelling, or primary production in Rivers Inlet could affect the OML in the future.

Shipboard velocity profiles collected in July 2018 are used to study coastal current in the south of Sri Lanka during the summer monsoon. The observations reveal that there is a narrow (~ 50 km wide) westward coastal current against the summer monsoon, separated the eastward southwest monsoon current (SMC) from the island of Sri Lanka. However, the climatological south Sri Lanka coastal current (SSLCC) is eastward following the direction of the SMC. The deviations between the observations and climatology of the SSLCC suggest its significant interannual variability. The dynamics of the westward SSLCC and its impact factors are thus focused on in this study. The results indicate that two main processes are responsible. First, the boreal summer intraseasonal oscillation (BSISO) plays an important role in the presence of westward SSLCC. The BSISO signal intensifies the wind strength east and south of Sri Lanka, reinforces the east India coastal current (EICC), and bends the SMC favoring occurrence of the westward SSLCC. Second, the upwelling Rossby wave signal propagates to Sri Lanka but stops at 82°E, which favors the Sri Lanka Dome developing. As the western flank of the SLD, the strengthened EICC flows southward and turns to west resulting in the westward SSLCC. Accordingly, the energy conversions by baroclinic and barotropic instability between mean flow and eddy are analyzed for both the westward and eastward SSLCC.

Extensive research has been conducted at Lake Tanganyika to understand its vulnerability to a warming climate and fishing pressure. However, much of this work has been restricted to the more accessible northern basin. Studies from a limited geographic region of the lake are insufficient to explain whole-lake dynamics of the world’s longest lake (~ 670 km N-S). While strong evidence suggests that lake warming has played a critical role in decreasing fish abundance, limnological changes associated with warming have not been investigated lake wide. This study used paleolimnological data from two deep-water sediment cores from southern Lake Tanganyika to determine whether changes observed in the northern and central basins are, in fact, representative of lake-wide phenomena. We infer a decrease in diatom concentration after ~ 3000 cal yrs BP to reflect a decrease in net primary productivity associated with decreasing convective mixing. In contrast, the episodic presence of benthic invertebrates (ostracodes and molluscs) at these deep sites between ~ 1800–500 cal yrs BP, along with high Mn, indicates episodic pulses of much deeper ventilation of the southern basin than has been recognized previously. The presence of periphytic diatom species and benthic invertebrates during periods of strong stratification suggests that the lake bottom was periodically ventilated by descending denser (cooler or more sediment-rich) influent waters along the steep slopes of the coastline. Fish fossil abundance also is correlated with the dominance of heavily silicified diatom taxa, which itself requires stronger wave activity and upwelling of deep, nutrient-rich water. Fossil diatom assemblages show P and Si gradients between the two sites. LT17-TANG17-6A shows a shift in dominance towards lightly silicified taxa (Nitzschia spp.) after ~ 200 cal yrs BP. LT17-TANG17-2A shows a reduction in concentration of mostly the lightly silicified taxa, with few periods having heavily silicified taxa. These results are indicative of a relative reduction in convective lake mixing but are not always coincident with temperature trends, suggesting local windiness may also be important for stratification history. Thus, changes in lake productivity in the southern basin appear to be climate mediated, but in ways not previously documented in the northern and central parts of the lake.

Spring waters with high-pCO2 content are widely distributed in the Sikhote-Alin region in Russia. Mukhen spa is one such spring located in the northern Sikhote-Alin region. This spa has two types of upwelling spring waters and exhibits distinct chemical signatures. One of the springs originates from a shallow aquifer and features hydrogen and oxygen isotopic ratios of meteoric water with a high 3He/4He ratio, whereas the other originates from a deeper aquifer and features a distinctly negative δ18O with a lower 3He/4He ratio. To understand this apparent discrepancy and the water circulation dynamics beneath Mukhen springs, we utilized all published data concerning the major solute elements and isotopic ratios of Mukhen spring waters and compared them with the He isotopic compositions on several springs in the far eastern region, which are newly analyzed in this study. The results show that the shallow aquifer comprises meteoric water that interacts with the crust enhanced by the gas component welling up from deep underground, while the fluid in deep aquifer fingerprinted the hydration reaction of silicate and involves a mantle component possibly delivered by a deep-seated fluid and/or gas upwelling along the tectonic fault through the western margin of the Sikhote-Alin region.

Coastal winds transport water masses and larval fish onshore or offshore which may influence estuarine recruitment, yet our understanding of the mechanism underlying this relationship is limited. Here, we combine datasets from a historical database of larval fish off southeast Australia with a high-resolution atmospheric reanalysis model to show that normalised abundance of coastally spawned larvae increased with weak to moderate upwelling favourable winds 14 days prior to sampling. The increase in abundance may reflect increased nutrient and plankton availability for larval fish. Normalised larval abundance decreased following strong upwelling favourable winds but increased after onshore (downwelling favourable) winds, due to wind-driven transport. By combining a commercial estuarine fisheries catch-rate dataset (4 species, 8 estuaries, 10 years) and the high-resolution atmospheric reanalysis model, we show that negative effects of upwelling favourable winds during the spawning period can be detected in lagged estuarine commercial fisheries catch rates (lagged by 2 - 8 years depending on species9 growth rates), potentially representing the same mechanism proposed for larval fish. Upwelling favourable winds in the southeast Australian region have increased since 1850 while onshore winds have decreased, which may reduce larval recruitment to estuaries. Coastal winds are likely an important factor for estuarine recruitment in the southeast Australian region and future research on the estuarine recruitment of fish should incorporate coastal winds.

Introduction: Salinas Bay is located in the warm pool of the Eastern Tropical Pacific (ETP), characterized by warm, shallow surface waters, a strong and shallow thermocline, and an important biological diversity. The primary productivity of the region is influenced by the coastal upwelling, which occurs during the boreal winter as a result of the strengthening of trade winds. Objective: To study the spatial and temporal dynamics of physical and chemical parameters at seven hydrographic stations in Salinas Bay, Costa Rica, through the analysis of CTD data, and relate the warm and cold events to the regional atmospheric conditions present when measuring the data. Methods: Seven hydrographic stations, sampled at Salinas Bay between August 2008 and December 2014, were selected. The variables processed for analysis are temperature, density, salinity, oxygen, chl-a and turbidity. Once the data was processed, 42 Hovmöller kind diagrams were plotted. Results: All variables, except turbidity, presented a seasonal periodicity associated with the upwelling. In general, colder and denser waters, higher salinity and chl-a concentrations and lower dissolved oxygen values were observed during the dry season, when the upwelling was active. Whereas, during the rainy season water masses were warmer and less dense, salinity and chl-a concentrations decreased and dissolved oxygen values tended to increase. Conclusions: The spatial and temporal dynamics of the hydrology in Salinas Bay was influenced by the coastal upwelling events. The region also presented an interannual variability associated with ENSO. Seasonal and interannual variability can counteract their effects on the oceanographic parameters when they coincide temporally. Resumen Introducción: Bahía Salinas se encuentra embebida en la piscina de agua cálida del Pacífico Tropical Oriental (PTO) o del Este (PTE), caracterizada por aguas superficiales cálidas, poco salinas, una termoclina fuerte y poco profunda y una importante diversidad biológica. La productividad primaria de la región está influenciada por el afloramiento oceánico, el cual se presenta durante el invierno boreal como resultado del fortalecimiento de los vientos alisios. Objetivo: Estudiar la dinámica espacial y temporal de parámetros físico-químicos en siete estaciones hidrográficas en Bahía Salinas, Costa Rica, a través del análisis de datos de CTD; y relacionar los eventos cálidos y fríos con las condiciones atmosféricas presentes al medir los datos. Métodos: Se muestrearon y seleccionaron siete estaciones hidrográficas en Bahía Salinas entre agosto de 2008 y diciembre de 2014. Las variables procesadas para su análisis son temperatura, densidad, salinidad, oxígeno, clorofila-a y turbidez. Una vez procesados los datos se graficaron 42 diagramas tipo Hovmöller. Resultados: Todas las variables, excepto la turbidez, presentaron una periodicidad estacional asociada al afloramiento. En general, se observaron aguas más frías y densas, mayores concentraciones de salinidad y clorofila-a y valores menores de oxígeno disuelto durante la estación seca, cuando el afloramiento estaba activo. Por el contrario, durante la estación lluviosa las masas de agua eran más cálidas y menos densas, las concentraciones de salinidad y clorofila-a disminuyeron y los valores de oxígeno disuelto tendieron a aumentar. Conclusiones: La dinámica espacial y temporal de la hidrología en Bahía Salinas fue influenciada por los eventos de afloramiento costero. La región también presentó una variabilidad interanual, como la asociada con el ENOS. La variabilidad estacional y la interanual pueden contrarrestar sus efectos sobre los parámetros oceanográficos cuando coinciden temporalmente.

The abundances and isotope compositions of molybdenum (Mo) and uranium (U) in ancient sediments are promising tracers of the redox state of the past ocean, whose basis lies in the environmentally dependent Mo and U isotope signatures in modern oceanic settings. Despite their dominance in oceanic budgets, the controls on the Mo-U systematics of upwelling margin sediments remain to be fully understood. Here we present a comprehensive sediment-porewater Mo and U isotope study in the Benguela upwelling system off Namibia, including the first dataset incorporating coupled Mo-U abundance and isotope analysis of both solid authigenic phases and porewaters. The investigated stations represent shelf-to-slope settings, which lie on the upper edge, within and below the oxygen minimum zone (OMZ) of the South Atlantic. The sediments across all stations share similar characteristics: both Mo and U show increasing authigenic enrichment with depth, coupled to an overall decrease in δ98Moauth (from ~2.0‰ to 1.3‰ and from ~2.0‰ to 0.3‰) and increase in δ238Uauth (from −0.18‰ to 0.05‰ and from −0.34‰ to −0.21‰). Nevertheless, the extents of Mo and U enrichment and associated isotopic fractionations display spatial variability across the OMZ, reflecting variations in local sedimentary redox conditions. Porewater Mo and U concentration patterns are more complex, exhibiting peaks in Mo and U abundance well in excess of seawater (up to 8 times seawater for Mo) associated with correlated shifts in isotope composition. As a result, porewaters exhibit a wide range in isotope compositions, between 0.90‰ and 2.79‰ for δ98Mo and between −1.74‰ and 0.26‰ for δ238U. Porewater gradients at the time of sampling are inconsistent with diffusion downwards across the sediment–seawater interface as a means of enrichment of the sediment-porewater system. Though these sampled conditions may represent only a snapshot, so that periodically more reducing conditions could lead to concentration gradients that do permit downward diffusion, the data are also readily explained by addition of Mo and U to the sediment-porewater system in particulate form, also under more reducing conditions than at the time of sampling. For example, sequestration of Mo and U to particulate matter as a result of the presence of intermittent sulfide, either in bottom water or in porewater right at the sediment–water interface, explains much of the geochemical and isotope data. The data thus suggest that the early diagenetic enrichment of Mo and U in sediments of upwelling margins is strongly governed by temporal redox fluctuations. Early diagenesis under these dynamic redox conditions on the Namibian upwelling margin are strongly reflected in Mo-U co-variation patterns, as well as anti-correlations between authigenic δ98Mo and δ238U in sediments. Overall, our new data demonstrate that early diagenetic processes on open-marine continental margins reproduce patterns previously observed for coupled Mo-U isotope systematics in restricted and semi-restricted basins, but via a different set of processes and with important implications for the use of such a coupled approach in the study of ancient marine anoxia.

Rangeland degradation is a global concern that is exacerbated by soil loss through water erosion. A deeper understanding of rainfall and runoff dynamics can assist in the development of sustainable management strategies. Current methods to measure surface runoff (e.g., natural runoff plots, rainfall simulation and overland flow experiments, modeling approaches) have many advantages but can be prohibitively expensive, may require considerable maintenance, and/or result in significant disturbance during installation. To address these limitations, we assessed a relatively new and underused method for monitoring runoff, the Upwelling Bernoulli Tube (UBeTube). The UBeTube is a low-cost, passive runoff monitoring method that estimates runoff from the height of water flowing out of a slot machined in the side of a vertical tube. In this study, we evaluated the UBeTube across a range of flow rates with three specific objectives: 1) calibrate the UBeTube measurements using clean water, 2) assess the impacts from varying sediment loads on UBeTube measurement accuracy, and 3) evaluate accuracy under conditions similar to those on undisturbed and disturbed rangelands. We found that properly calibrated UBeTubes could be a relatively accurate runoff monitoring method on rangelands (mean percent error = 7.7% clean water calibration, 34.1% sediment loading, 35.2% undisturbed overland flow, 17.7% disturbed overland flow). UBeTubes provide an alternative method to monitor runoff on rangelands that can augment current methods by providing near real-time measurements of runoff generated during natural precipitation events. Easily and rapidly deployed across the landscape, UBeTubes could allow for the relative measurement of spatially variable hydrologic dynamics and serve as another source of information for management decision-making processes and the creation of sustainable strategies for rangeland development.

Cnidarian jellyfish can be dominant players in the food webs of highly productive Eastern Boundary Currents (EBC). However, the trophic role of inconspicuous hydromedusae in EBCs has traditionally been overlooked. We collected mesozooplankton from five stations along two cross-shelf transects in the Northern California Current (NCC) during winter and summer of 2018–2019. We analyzed gut contents of 11 hydromedusan species and the prey community to (i) determine prey resource use by hydromedusae and (ii) determine temporal shifts in the trophic niche of hydromedusae, focusing on the two most collected species (Clytia gregaria and Eutonina indicans). Hydromedusae in the NCC fed mostly on copepods, appendicularians and invertebrate larvae. Nonmetric multidimensional scaling of hydromedusan diets showed seasonal shifts in prey resource driven by the abundant C. gregaria, which fed mostly on copepod eggs during winter and fed mostly on appendicularians and copepods during summer. Prey selectivity for copepod eggs increased during winter for C. gregaria and E. indicans. Intriguingly, theoretical ingestion rates show that both species acquire similar amounts of carbon during upwelling and nonupwelling conditions. Hydromedusae’s consistent presence and predation impact across seasons may lead to significant effects in carbon and energy transfer through the NCC food web.

The climate variability induced by the El Nino-Southern Oscillation (ENSO) cycle drives significant changes in the physical state of the tropical Western Pacific, which has important impacts on the upper ocean carbon cycle. During 2015–2016, a super El Nino event occurred in the equatorial Pacific. Suspended particulate matter (SPM) data and related environmental observations in the tropical Western Pacific were obtained during two cruises in Dec. 2014 and 2015, which coincided with the early and peak stages of this super El Nino event. Compared with the marine environments in the tropical Western Pacific in Dec. 2014, an obviously enhanced upwelling occurred in the Mindanao Dome region; the nitrate concentration in the euphotic zone almost tripled; and the size, mass concentration, and volume concentration of SPM obviously increased in Dec. 2015. The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths, even into the euphotic zone, which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone. These results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Nino events. In the context of the ENSO cycle, if predicted changes in biogenic particles occur, the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%, ultimately affecting the regional and possibly even global carbon cycle. This paper highlights the prospect for long-term prediction of the impact of a super El Nino event on the global carbon cycle and has profound implications for understanding El Nino events.

Poleward undercurrents are well-known features in eastern boundary upwelling systems. In the California Current upwelling system, the California poleward undercurrent has been widely studied, and it has been demonstrated that it transports nutrients from the equatorial waters to the northern limit of the subtropical gyre. However, in the Canary Current upwelling system, the Canary intermediate poleward undercurrent (CiPU) has not been properly characterized, despite recent studies arguing that the dynamics of the eastern Atlantic Ocean play an important role in the Atlantic meridional overturning circulation, specifically on its seasonal cycle. Here, we use trajectories of Argo floats and model simulations to characterize the CiPU, including its seasonal variability and its driving mechanism. The Argo observations show that the CiPU flows from 26°N, near Cape Bojador, to approximately 45°N, near Cape Finisterre and flows deeper than any poleward undercurrent in other eastern boundaries, with a core at a mean depth of around 1000 dbar. Model simulations manifest that the CiPU is driven by the meridional alongshore pressure gradient due to general ocean circulation and, contrary to what is observed in the other eastern boundaries, is still present at 1000 dbar as a result of the pressure gradient between the Antarctic Intermediate Waters in the south and Mediterranean Outflow waters in the north. The high seasonal variability of the CiPU, with its maximum strength in autumn and minimum in spring, is due to the poleward extension of AAIW, forced by Ekman pumping in the tropics.

18 pages, 9 figures.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY), Ocean acidification has critical impacts on marine ecosystems, but presents knowledge gaps on the ecological impacts requiring large-scale monitoring of physicochemical conditions to predict biological responses to ocean pH projections. The threat is especially significant in coastal regions like upwelling areas which are more sensitive and appear to respond more rapidly to anthropogenic perturbations. These ecosystems, such as the northwest coast of the Iberian Peninsula are characterized by complex physical and biogeochemical interactions, supporting enormous biological productivity and productive fisheries. The distribution of pH in upwelling systems has high variability on short temporal and spatial scales preventing a complete picture of acidification, which exhibit long-term pH rates markedly different from the measured in open waters. This motivation to significantly expand the coverage of pH monitoring in coastal areas has driven us to develop an autonomous pH monitoring instrument (from now on SURCOM) based on the Honeywell Durafet® pH electrode. A relevant feature is that SURCOM transmits near real-time pH and temperature measurements every 10.5 min through SIGFOX®, a low-power, low-bandwidth network for data transmission. This very careful design allows us to achieve a very low power consumption for the complete system resulting in 3 years of full autonomy with no other need than external cleaning and calibration. In this paper we describe the setup and the data set obtained by a SURCOM instrument over 240 days in a highly productive and dynamic coastal ecosystem, the Rıá de Arousa embayment, providing valuable information on the performance of these low-cost and highly stable sensors, with potential for improving the pH variability description in nearshore systems and for reinforcing the monitoring-modeling of coastal acidification, Funding for AV was received from AtlAzul (0755_ATLAZUL_6_E) co-funded by the INTERREG V-A Spain-Portugal Cooperation Program (POCTEP) 2014-2020. Funding for XP comes from Observatorio TIAMAT project (2715-2021) funded by the Autonomous Agency of National Parks of the Ministry for Ecological Transition and Demographic Challenge. This work has also been supported from the MarRISK project (0262_MarRISK_1_E) co-funded by INTERREG V-A Spain-Portugal Cooperation Program (POCTEP) 2014-2020 and from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 820989 (COMFORT). This work was also contributed by WATER:iOS CSIC PTI