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While moderate wind and wave conditions prevail in the eastern equatorial Pacific, modeling waves in this area remains challenging due to the presence of multiple wave systems converging from different parts of the ocean. This area is covered by swells originated far away including the storm belts of both hemispheres, coexisting with local generation due to the regular action of both the southern trade winds and the wind jets from Central America. In this context, our ability to predict waves in the area depends on the overall quality (i.e., at Pacific scale) of the meteorological input, and also on the skills of the wave model itself. Clearly any error at the remote generation areas translates into larger errors the further waves go, especially if attention is focused on coastal areas. A relevant aspect is that the traditional integral parameters do not offer the possibility to properly assess the errors associated with the different parts of the spectrum (e.g., wind sea and swell). To gain insight in this direction, we make use of partitioning techniques, which enables us to neatly cross-assign and evaluate three spectral components. Not surprisingly, the performance for the swell part is lower than that of the corresponding wind sea. This is further explored with a couple of tests modifying both the wind input and the wave model physics. We find that although at first sight the initial scheme (i.e., ST4) seems to provide the better estimate, the spectral analysis reveals a substantial underestimation of wind sea, compensated with a substantial overestimation of swell. This suggests a problem with too high winds and wave generation in the storm belts together with a likely lack of dissipation or dispersion of swell. In turn, local waves are generally underestimated due to a corresponding underestimation of the local winds. This insight emphasizes the need and advantages of evaluation methods able to look at the different sectors of the wave spectrum.

Observations from six Lagrangian Surface Wave Instrument Float with Tracking (SWIFT) drifters in January-February 2020 in the northwestern tropical Atlantic during the Atlantic Tradewind Ocean-atmo...

The westerlies and trade winds over the South Atlantic and Indian Ocean are important drivers of the regional oceanography around southern Africa, including features such as the Agulhas Current, the Agulhas leakage, and the Benguela upwelling. Agulhas leakage constitutes a fraction of warm and saline water transport from the Indian Ocean into the South Atlantic. The leakage is stronger during intensified westerlies. Here, we analyze the wind stress of different observational and modeled atmospheric data sets (covering the last 2 millennia, the recent decades, and the 21st century) with regard to the intensity and position of the southeasterly trades and the westerlies. The analysis reveals that variations of both wind systems go hand in hand and that a poleward shift of the westerlies and trades and an intensification of westerlies took place during the recent decades. Furthermore, upwelling in South Benguela is slightly intensified when trades are shifted poleward. Projections for strength and position of the westerlies in the 21st century depend on assumed CO2 emissions and on their effect relative to the ozone forcing. In the strongest emission scenario (RCP8.5) the simulations show a further southward displacement, whereas in the weakest emission scenario (RCP2.6) a northward shift is modeled, possibly due to the effect of ozone recovery dominating the effect of anthropogenic greenhouse forcing. We conclude that the Agulhas leakage has intensified during the last decades and is projected to increase if greenhouse gas emissions are not reduced. This will have a small impact on Benguela upwelling strength and may also have consequences for water mass characteristics in the upwelling region. An increased contribution of Agulhas water to the upwelling water masses will import more preformed nutrients and oxygen into the upwelling region.

Four trawl-resistant bottom mounts, with acoustic Doppler current profilers (ADCPs) embedded, were deployed in the Karimata Strait from November 2008 to June 2015 as part of the South China Sea-Indonesian Seas Transport/Exchange and Impact on Seasonal Fish Migration (SITE) Program, to estimate the volume and property transport between the South China Sea and Indonesian seas via the strait. The observed current data reveal that the volume transport through the Karimata Strait exhibits significant seasonal variation. The winteraveraged (from December to February) transport is–1.99 Sv (1 Sv=1×106 m3/s), while in the boreal summer (from June to August), the average transport is 0.69 Sv. Moreover, the average transport from January 2009 to December 2014 is–0.74 Sv (the positive/negative value indicates northward/southward transport). May and September are the transition period. In May, the currents in the Karimata Strait turn northward, consistent with the local monsoon. In September, the southeasterly trade wind is still present over the strait, driving surface water northward, whereas the bottom flow reverses direction, possibly because of the pressure gradient across the strait from north to south.

The tropical Atlantic upper-ocean circulation experiences multiannual to decadal changes associated with different climate modes and is simultaneously adjusting to climate warming. The most energetic current in the tropical Atlantic is the Equatorial Undercurrent (EUC), which flows eastwards along the Equator. On the basis of long-term moored observations, we show that the EUC strengthened by more than 20% from 2008 to 2018. The intensification of the EUC is associated with increasing subsurface oxygen concentrations and a thickening of the upper-ocean oxygenated layer in the equatorial Atlantic. These changes counteract climate-warming-induced deoxygenation in the region. The EUC strengthening is found to be mainly forced by trade wind changes in the western tropical North Atlantic. A 60-yr dataset reveals that the recent oxygen increase in the upper equatorial Atlantic is associated with multidecadal variability. This variability is characterized by low oxygen concentrations in the 1990s and early 2000s, and high oxygen concentrations in the 1960s and 1970s. The observed oxygen variability seems to be linked to a compression and expansion of the habitat of tropical pelagic fish, and must be accounted for when evaluating the possible consequences of deoxygenation for marine ecosystems and fisheries. Recent strengthening of the Equatorial Undercurrent counteracts warming-induced deoxygenation in the equatorial Atlantic, according to an analysis of long-term moored observations.

The causes of the seasonal cycle of vertical turbulent cooling at the base of the mixed layer are assessed using observations from moored buoys in the tropical Atlantic Intertropical Convergence Zone (ITCZ) (4°N, 23°W) and trade wind (15°N, 38°W) regions together with mixing parameterizations and a one-dimensional model. At 4°N the parameterized turbulent cooling rates during 2017–2018 and 2019 agree with indirect estimates from the climatological mooring heat budget residual: both show mean cooling of 25–30 W m (Formula presented.) during November–July, when winds are weakest and the mixed layer is thinnest, and 0–10 W m (Formula presented.) during August–October. Mixing during November–July is driven by variability on multiple time scales, including subdiurnal, near-inertial, and intraseasonal. Shear associated with tropical instability waves (TIWs) is found to generate mixing and monthly mean cooling of 15–30 W m (Formula presented.) during May–July in 2017 and 2019. At 15°N the seasonal cycle of turbulent cooling is out of phase compared to 4°N, with largest cooling of up to 60 W m (Formula presented.) during boreal fall. However, the relationships between wind speed, mixed layer depth, and turbulent mixing are similar: weaker mean winds and a thinner mixed layer in the fall are associated with stronger mixing and turbulent cooling of SST. These results emphasize the importance of seasonal modulations of mixed layer depth at both locations and shear from TIWs at 4°N.

Long-term trends in the sea surface temperature in the Canary upwelling zone and their causes are analyzed on the basis of satellite data from the 1980s until the present. It is shown that the wind activity has strengthened near the northwestern African coast during last 30 years, which is accompanied by local intensification of wind-driven upwelling. The northeastern trade wind weakens in the open Tropical Atlantic, along with the horizontal heat advection in the upper ocean layer, which leads to a decrease in the area of the upwelling waters. As a result, both tendencies partly compensate one another when the temperature is averaged over the region in the northeastern Tropical Atlantic (between 10°–30° N, 10°–25° W).

Sea level (SL) is rising in Puerto Rico due to regional influences from weaker trade winds, in addition to global influences of thermal expansion and polar ice melt. The linear increase of SL has steepened in recent decades from +0.175 to +0.725 cm/yr. The faster rate of SL rise is partly attributed to diminishing ice volume (r = −0.80), notwithstanding a recent decline in the Atlantic Multi-decadal Oscillation. A sophisticated point-to-field regression analysis (N = 5980) demonstrates that daily fluctuations of SL in Puerto Rico are significantly enhanced by locally warmer sea temperatures via reduced evaporation, and correspond with lower air pressure accompanying late summer storms. These features point to regional air-sea interactions that affect SL rise over and above the background global signal. Extrapolating these trends, a rise of more than 0.3 m is expected by 2050.

Malaysian Airlines Flight MH370 disappeared on 8 March 2014, while flying from Kuala Lumpur to Beijing. A flaperon from the flight was found on Reunion Island in July 2015. Two more confirmed pieces of debris were found in Mauritius and Tanzania, and 19 unconfirmed items were found off Mozambique, South Africa, and Madagascar. Drift buoys originating from the designated underwater search area arrived in Reunion Island, Mauritius, and Tanzania. Some of these buoys took a similarly long time as did real debris to reach these destinations, following a heading northeast and then west. For the present study, a maritime object drift prediction model was developed. “High resolution surface currents, Stokes drift, and winds” were processed, and a series of model experiments were constructed. The predicted trajectories of the modeled objects were similar to the observed trajectories of the drift buoys. Many modeled objects drifted northward then westward, ending up in Reunion Island, Mauritius, and Tanzania with probabilities of 5‰, 5‰, and 19‰, respectively. At the end of the simulation, most objects were located near 10°S in the western Indian Ocean. There were significant differences between experiments with different leeway factors, possibly because of the influence of southeast trade winds. The north part of the underwater search area is most likely to be the crash site, because the predicted trajectories of objects originating here are consistent with the many pieces of debris found along the east coast of Africa and the absence of such findings on the west coast of Australia.

Interannual and long-term variability of the low level jetstream (LLJ) of the Asian summer monsoon during June to September was studied using reanalysis wind data. In order to study the variability, the domain of the LLJ covering the Indian and west Pacific Oceans was divided into six regions (boxes) based on their physical characteristics. The long term variability of LLJ and its relation with Indian monsoon rainfall and El Nino index were analysed. The low level circulation over Indian Ocean becomes weak during the positive phase of El Nino Southern Oscillation leads to warmer sea surface temperature over Indian Ocean. The strength of the low level jet over India depends on the convective heating of the atmosphere and not on the strength of the south Indian Ocean trade wind (ITz) which remains a passive component of the LLJ. The LLJ flow through peninsular India is weaker and the flow south of peninsular India is stronger during the recent decades in association with increasing number of break monsoon days. The cross equatorial flow over west Pacific Ocean has statistically significant increasing trend related to the increasing convection in the west Pacific Ocean.

Waves are the dominant influence on coastal morphology and ecosystem structure of tropical islands. The geographical positioning of Mauritius near to the Tropic of Capricorn ensures that the eastern regions benefit from the persistent southeast trade winds which influence the incoming surface waves. In this study, we present the high dependence of the wave regimes of windward offshore site on the trade winds. The higher occurrence of incoming waves in the winter season directed in the southeast direction indicates that the trade winds are more prevalent in the winter season. Storms within the extratropical South Atlantic, Indian and Pacific oceans generally propagate towards the east such that extratropical South Atlantic swell energy spreads through the entire Indian Ocean. Since waves are very directional and tend to get shadowed by land masses, Mauritius situated in the line of sight from those sources end up in the shadow region due to the geographical location of Reunion island. In this study, we support the explanation on how the western region of the island gets influenced by episodic swell events. A detailed wave energy resource assessment is provided for different targeted coastal environments around the island. It is revealed that the mean wave power observed in the summer season at one of the sites can attain 28.8 kW/m and is found to be lower as compared to the winter season (31.7 kW/m).

Five-year (2010 to 2014) sea surface temperature (SST) data from the Advanced Very High Resolution Radiometer (AVHRR) are used to study the effects of the Australian summer monsoon on SST diurnal variation (DV) over the Australian North-Western shelf (NWS, defined as 105°E-125°E, 25°S-10°S). Strong DV events identified with amplitude of 0.5-2K were observed over the NWS. A double-peak seasonal pattern of DV is obtained, with the strongest DV occurring in February/March and October/November. This seasonal DV pattern over the NWS is largely due to the Australian summer monsoon, which reduces the easterly trade wind during the summer monsoonal period, favouring the development of SST DV. Since the monsoon region is distributed globally in the tropical oceans, in the western and eastern North Pacific, as well as in the southern Indian Ocean, we anticipate that strong SST DV may also exist in these parts of coastal oceans.

International audience; This paper reports on two three-months field experiments carried out in the Ouano lagoon, New Caledonia. This channel-type lagoon, exposed to meso-tides, south pacific swells and trade winds, has been monitored thanks to a network of currents profilers to understand the dynamics of the lagoon waters. Four typical circulation patterns have been identified, covering all together more than 90% of the survey period. These patterns are mainly driven by the waves and wind features. In particular, obliquely incident waves or strong winds blowing over a sufficient period are able to reverse the typical circulation pattern. The analysis of the vertical structure of the currents through passages shows the regular presence of a nearly linear vertical shear within the water column.

The frequency of central Pacific (CP) El Nino events displays strong decadal-variability but the associated dynamics are unclear. The Interdecadal Pacific Oscillation (IPO) and the Tropical Pacific Decadal Variability (TPDV) are two dominant modes of tropical Pacific decadal variability that can interact with high-frequency activities. Using a 500-year control integration from the Geophysical Fluid Dynamics Laboratory Earth System Model, we find that the difference in mean state between the low-frequency and high-frequency CP El Nino periods is similar to the decadal background condition concurrently contributed by a negative IPO and a positive TPDV. This decadal state features strengthened trade winds west of the International Date Line and anomalous cool sea surface temperatures across the central tropical Pacific. As such, positive zonal advection feedback is difficult to be generated over the central-to-western tropical Pacific during the CP El Nino developing season, resulting in the low CP El Nino frequency.

Recent advances in tropical Pacific climate variability have focused on understanding the development of El Nino-Southern Oscillation (ENSO) events, specifically the types or “flavors" of ENSO (i.e., central vs. eastern Pacific events). While precursors to ENSO events exist, distinguishing the particular flavor of the expected ENSO event remains unresolved. This study offers a new look at ENSO predictability using South Pacific atmospheric variability during austral winter as an indicator. The positive phase of the leading mode of South Pacific sea level pressure variability, which we term the South Pacific Oscillation (SPO), exhibits a meridional dipole with a(n) (anti-)cyclonic anomaly dominating the subtropics (extratropics/high latitudes). Once energized, the cyclonic anomalies in the subtropical node of the SPO weaken the southeasterly trade winds and promote the charging of the eastern equatorial Pacific Ocean, giving rise to eastern Pacific ENSO events. Indeed, the type of ENSO event can be determined accurately using only the magnitude and phase of the SPO during austral winter as a predictor (18 out of 23 cases). The SPO may also play a role in explaining the asymmetry of warm and cold events. Collectively, our findings present a new perspective on ENSO-South Pacific interactions that can advance overall understanding of the ENSO system and enhance its predictability across multiple timescales.

The South Asian summer monsoon (SASM) during the mid-Piacenzian is analyzed through climate modelling with CAM4. The model results reveal a non-uniform spatial difference in the SASM during the mid-Piacenzian compared to the pre-industrial era, with the SASM being more intense north of ~20°N but weaker south of ~20°N. In particular, summer precipitation is higher in South Asia north of ~20°N, accompanied by anomalous low-level southwesterlies from the Arabian Sea, whereas the precipitation is lower in South Asia south of ~20°N, with anomalous low-level easterlies. These differences in the SASM are related to changes in sea level pressure (SLP) due to the different boundary conditions between the two periods. Further analysis isolates the climate effects of the different boundary conditions and indicates the combined difference in atmospheric carbon dioxide concentration and SST to be the most important factor in this difference in the SASM through the changes in SLP. By comparison, the differences in vegetation and topography have limited effects. The availability of geological evidence is relative greater in northern India than in southern India, and comparison with this geological evidence shows the simulated monsoon climate to be qualitatively consistent with it, particularly for the wetter climate in northern India.

The Kimberley-Territory division includes the rugged Kimberley coast and the low western and northern coast of the Northern Territory (NT). This is a remote difficult-to-assess coast dominated by meso through mega-tides, low waves and a monsoonal climate, all exposed to trade winds and periodic tropical cyclones. The Kimberley coast is dominated by its deeply dissected joint-aligned geology and is a predominately steep rocky shore with small usually embayed beaches and extensive mangroves in sheltered areas. The NT coast is low with several rivers building deltas and extensive tide-dominated beaches and their wide tidal flats, with mangroves occupying all lower energy section of the coast. Barrier development is limited and usually restricted to regressive beach-foredune ridges, with a few areas of dune transgression. The chapter describes the geology, climate and coast and biological processes that have contributed to the formation of the coast.

The westerlies and trade winds over the South Atlantic and Indian Ocean are important drivers of the regional oceanography around Southern Africa, including features such as the Agulhas current, the Agulhas leakage and the Benguela upwelling. The Agulhas leakage is the transport of warm and saline water from the Indian Ocean into the South Atlantic. The leakage is stronger during intensified westerlies and probably also when the wind systems are shifted poleward. Here we analyzed the wind stress of different observational and modelled atmospheric data sets (covering the last two millennia, the recent decades and the 21st century) with regard to the intensity and position of the south-easterly trades and the westerlies. The analysis reveals that variations of both wind systems go hand in hand. A poleward shift and intensification of westerlies and trades took place during the recent decades. Furthermore, the upwelling in South Benguela slightly intensified and the characteristics of the water masses fed into the upwelling region changed with a poleward shift of the trades. Projections for strength and position of the westerlies in the 21st century depend on assumed CO2 emissions. In the strongest emission scenario a further southward displacement will occur, whereas a northward shift is modelled in the weakest emission scenario, possibly due to the dominating driving effect of ozone recovery. Thus, the Agulhas leakage has intensified during the last decades and is projected to increase if greenhouse gas emission are not reduced. This will have a small impact on Benguela upwelling strength, but will have consequences for water mass characteristics in the upwelling region. An increased contribution of Agulhas water to the upwelling feed water masses will import more preformed nutrients and oxygen into the upwelling region.

Recent paleoclimatic studies suggest that changes in the tropical rainbelt across the Atlantic Ocean during the past two millennia are linked to a latitudinal shift of the Intertropical Convergence Zone (ITCZ) driven by the Northern Hemisphere (NH) climate. However, little is known regarding other potential drivers that can affect tropical Atlantic rainfall, mainly due to the scarcity of adequate and high-resolution records. In this study, we fill this gap by reconstructing precipitation changes in Northeastern Brazil during the last 2,300 years from a high-resolution lake record of hydrogen isotope compositions of plant waxes. We find that regional precipitation along the coastal area of South America was not solely governed by north-south displacements of the ITCZ due to changes in NH climate, but also by the contraction and expansion of the tropical rainbelt due to variations in sea surface temperature and southeast trade winds in the tropical South Atlantic Basin., We thank Fanny Kaczmar (LOCEAN-UPMC) and Ralph Kreutz (MARUM) for their support during the analyses, Igor M. Venancio (INPE) for comments about this paper. The lipid extractions were supported by LOCEAN/IRD. The isotope analyses were supported by the DFG-Research Center/Cluster of Excellence, “The Ocean in the Earth System” at MARUM - Center for Marine Environmental Sciences. This work was supported by the Fundação de Amparo a Pesquisa do Estado de São Paulo (FAPESP), Brazil through NSF Dimensions-Biota FAPESP grant 2013/50297 and PIRE NSF-FAPESP Grants 2017/50085-3 to F.W.C as well as the post-doc fellowship to V.F.N (2016/15807-5) and the US National Science Foundation NSF grants AGS-1303828 and OISE-1743738 to MV and 1103403 to R.L.E and H.C. We thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Brazil (CAPES) fellowship to G.U. Grant 99999.012754/2013-07 as well as the post-doc fellowship through the Postgraduate Program on Geochemistry and Geotectonics, Geoscience Institute of the University of São Paulo.

Previous studies have revealed a connection between springtime sea surface temperature (SST) in the tropical northern Atlantic (TNA) and the succeeding wintertime El Niño–Southern Oscillation (ENSO). The present analysis demonstrates that the linkage between springtime TNA SST and the following ENSO experiences an obvious interdecadal change around the early 1980s, with the connection being weak before but significant after. After the early 1980s, springtime positive TNA SST anomalies induce an anomalous cyclone over the northeastern subtropical Pacific and an anomalous Walker circulation with a descending branch over the tropical central-eastern Pacific. This leads to anomalous cold SST in the northeastern Pacific and an anomalous anticyclone over the western-central tropical Pacific, with anomalous easterlies to the equatorward side. As such, springtime TNA SST anomalies are followed by wintertime ENSO after the early 1980s. In contrast, before the early 1980s, anomalous cold SST in the northeastern Pacific and related anomalous easterlies over the western-central tropical Pacific are weak, corresponding to springtime positive TNA SST anomalies and resulting in a weak linkage between springtime TNA SST and the succeeding wintertime ENSO. Further investigation implies that the change in the TNA SST–ENSO relationship is probably due to a change in springtime mean precipitation over the tropical Atlantic and South America.

Sampling was conducted at 31 sites in the western Pacific Ocean from 2000 to 2001 with the aim of collecting plastic fragments with a neuston net (mesh size: 1.00 mm × 1.64 mm). Small plastic fragments including microplastics (small fragments in the size range of 1.1–41.8 mm) were collected at multiple survey sites. Waters with high densities of small fragments were observed between 20°N and 30°N to the south of Japan and between 20°S and 30°S to the northeast of New Zealand (maxima of 6.63 × 102 and 2.04 × 102 pieces/ha, respectively). These waters are located to the west of the Ekman convergence zones related to trade winds in the subtropical gyres of the North and South Pacific Oceans. Nearly no small plastics were observed in the tropical circulation of the western Pacific Ocean., 2000年から2001年にかけて太平洋西部海域の31地点でニューストンネット（目合1.00mm×1.64mm）によるプラスチック微小片の採集を行った。マイクロプラスチック(5mm以下)を含むプラスチック微小片は，日本の南の北緯20—30度の海域とニュージーランド北東の南緯20—30度の海域で高密度に採集され（各々最高で6.63×102と2.04×102個/ha），これらの海域は北太平洋と南太平洋における亜熱帯循環内の漂流物収束帯の西端に位置する。赤道付近の熱帯循環内の採集点ではほとんど採集されなかった。

Interannual and longer timescale variations of the North Equatorial Countercurrent (NECC) in the western Pacific are investigated using the multi-decade (1960-2014) hindcast by the Ocean general circulation model for the Earth Simulator (OFES). The OFES-simulated sea level and upper ocean circulation changes show favorable comparisons with available tide gauge data and repeat hydrographic surveys along the 137oE meridian. An empirical orthogonal function (EOF) analysis reveals that the low-frequency NECC variability is dominated by two distinct modes. The first mode fluctuates interannually and shows strengthening and southward migration of the NECC concurrent with the development of El Nino events. Unlike the extra-tropical western Pacific Ocean circulation variability controlled by wind forcing west of the dateline, the interannual NECC variations are forced by equatorial wind forcing cumulative across the entire Pacific basin. The second mode of the NECC variability has a inter-decadal timescale and is characterized by NECC's progressive weakening in strength, migrating poleward, and broadening in width over the past 50 years. These long-term changes in NECC are caused by the corresponding changes in the trade wind system that weakened and expanded poleward in the past half a century across the Pacific basin. This article is protected by copyright. All rights reserved.

The Pacific trade winds have been strengthening over the past two decades, but until now the cause of this has not been known. Now research shows that sulfate aerosols caused the western North Pacific Ocean to warm, leading to the trade-wind intensification.

One year of deep-water wave hourly records collected by a buoy deployed off Ceará state, northeastern Brazilian coast, were used to estimate some regional wave climate characteristic sand annual cycles. Waves generated by four wind sources were identified. Southeastern direction showed to be the most effective, especially in the period from June to November due to southeast trade winds system intensification. Several dispersive arrivals of north Atlantic swell were recorded, and their generation zones were identified, which allows determining the region of main sources of these northern waves. Analysis of sea storms showed that although most of them had southeast direction, they could also come from the north. These northern storms sometimes are highly energetic, leading to damage in coastal structures. Only 37 records in the analyzed dataset around 0.4% of the total contained rogue waves. Although the number of occurrences of rogue waves was small, all of them were higher than 2.5 m. One year of deep-water wave hourly records collected by a buoy deployed off Ceará state, northeastern Brazilian coast, were used to estimate some regional wave climate characteristic sand annual cycles. Waves generated by four wind sources were identified. Southeastern direction showed to be the most effective, especially in the period from June to November due to southeast trade winds system intensification. Several dispersive arrivals of north Atlantic swell were recorded, and their generation zones were identified, which allows determining the region of main sources of these northern waves. Analysis of sea storms showed that although most of them had southeast direction, they could also come from the north. These northern storms sometimes are highly energetic, leading to damage in coastal structures. Only 37 records in the analyzed dataset around 0.4% of the total contained rogue waves. Although the number of occurrences of rogue waves was small, all of them were higher than 2.5 m. 2020-11-01

The present manuscript analyses the role of the submesoscale hydrodynamic patterns close to the coastal margin of the Strait of Gibraltar in the exchange of properties between the western side of the Strait and the western Alboran Sea. To achieve this goal a multi-approach analysis was performed using several datasets obtained during an oceanographic survey, drifters, satellite data and numerical simulation experiments. Three areas were identified: Trafalgar, Camarinal and the north-western corner of the Alboran Sea, in which the water exhibits a high residence time and relatively high phytoplankton concentrations. In addition, evidence of transport processes that take place along the coastal margin is shown between Trafalgar and the Alboran Sea. These transport processes seem to connect the phytoplankton that grows in the Gulf of Cadiz strip, in response to the nutrients supplied by the Guadalquivir River, to the phytoplankton populations in the western Alboran Sea. Furthermore, the transport of properties along this margin is clearly disrupted by strong and persistent easterly winds.

Surface chlorophyll-a (Chl-a) distribution have been analyzed with seasonal variation during southeast monsoon in southern part of Makassar Strait and Flores Sea. Satellite data of Landsat-8 is applied to this study to formulate the distribution of chlorophyll concentration during monsoonal wind period. The distribution of chlorophyll concentration was normally peaked condition in August during southeast monsoon. Satellite data showed that a slowdown in the rise of the distribution of chlorophyll in September with a lower concentration than normal is likely due to a weakening the strength of southeast trade winds during June – July – August 2016. Further analysis shows that the southern part of the Makassar strait is likely occurrence of upwelling characterized by increase in surface chlorophyll concentrations were identified as the potential area of fishing ground.

The southern Caribbean Sea experiences strong coastal upwelling between December and April due to the seasonal strengthening of the trade winds. A second upwelling was recently detected in the southeastern Caribbean during June–August, when local coastal wind intensities weaken. Using synoptic satellite measurements and in situ data, this mid-year upwelling was characterized in terms of surface and subsurface temperature structures, and its mechanisms were explored. The mid-year upwelling lasts 6–9 weeks with satellite sea surface temperature (SST) ~1–2° C warmer than the primary upwelling. Three possible upwelling mechanisms were analyzed: cross-shore Ekman transport (csET) due to alongshore winds, wind curl (Ekman pumping/suction) due to wind spatial gradients, and dynamic uplift caused by variations in the strength/position of the Caribbean Current. These parameters were derived from satellite wind and altimeter observations. The principal and the mid-year upwelling were driven primarily by csET (78–86%). However, SST had similar or better correlations with the Ekman pumping/suction integrated up to 100 km offshore (WE100) than with csET, possibly due to its influence on the isopycnal depth of the source waters for the coastal upwelling. The mid-year upwelling was not caused by dynamic uplift but it might have been enhanced by the seasonal intensification of the Caribbean Current during that period.

Cruise data sets, satellite remote sensing observations, and model data analyses are combined to highlight the existence of a coastal surface poleward flow in the southwest of Madagascar: the Southwest MAdagascar Coastal Current (SMACC). The SMACC is a relatively shallow (

Previous studies reported that positive phases of the Indian Ocean Dipole (IOD) tend to accompany El Nino during boreal autumn. Here we show that the El Nino/IOD relationship can be better understood when considering the two different El Nino flavors. Eastern-Pacific (EP) El Nino events exhibit a strong correlation with the IOD dependent on their magnitude. In contrast, the relationship between Central-Pacific (CP) El Nino events and the IOD depends mainly on the zonal location of the sea surface temperature anomalies rather than their magnitude. CP El Nino events lying further west than normal are not accompanied by significant anomalous easterlies over the eastern Indian Ocean along the Java/Sumatra coast, which is unfavorable for the local Bjerknes feedback and correspondingly for an IOD development. The El Nino/IOD relationship has experienced substantial changes due to the recent decadal El Nino regime shift, which has important implications for seasonal prediction.

The upwelling at Punta Gallinas in the Guajira Peninsula (Colombian Caribbean) was studied from the point of view of the Mathematical Morphology using 10 years of monthly composite MODIS-SST imagery. Among all the morphological operators, the skeleton is widely used to compute the axis of the of the SST fields for the observed upwelling events. The skeleton is characterized by means of the Geometrical Theory of Measurement using the fractal dimension. The upwelling in the area is driven by the dynamic of the ITCZ (InterTropical Convergence Zone) and the relationship between the area and the East-West component of the trade winds has a lag of about 4 months. It has been found that the fractal dimension of the skeleton and the area of the upwelling are related. Some relationship was found between the fractal dimension of the skeleton (its complexity) and the Southern Oscillation Index by means of linear regression and cross-spectral analysis finding coherent energy at 1 year, 6 months and in the low frequency band. Finally, a sensitivity analysis between fractal dimension and threshold SST points out to take an extreme care at the time of fixing the last one.

Even though the vital role of thermocline fluctuation in El Nino–Southern Oscillation (ENSO) cycle has been established previously, the direct relationship between the thermocline depth and sea surface temperature (SST) anomalies in the equatorial Pacific is yet to be fully understood, especially its seasonality. Thermocline depth anomalies have been found to lead SST anomalies in time with a longitude-dependent delay, but our study also suggests that the relationship shows considerable seasonal dependency and is strongest (weakest) during the boreal spring (summer). Over the eastern equatorial Pacific where there is least delay (compared to that in the western and central Pacific), the connection between thermocline and SST is the weakest during the boreal spring. This feature may be one of causes for ENSO spring persistence barrier. Furthermore, the thermocline-SST connections exhibit significant decadal variations, which are remarkably consistent with the decadal changes in the persistence barrier of SST anomalies over the eastern Pacific. It is also found that the decadal shift in the timing of the thermocline-SST connection barrier is caused by the changes in the seasonal cycle of tropical trade winds and thermocline depths.

This paper presents a new style of bedload parting from western Torres Strait, northern Australia. Outputs from a hydrodynamic model identified an axis of bedload parting centred on the western Torres Strait islands (~142°15′E). This bedload parting is similar to others documented from mixed tidal regimes as it is driven dominantly by the O1, K1 and M2 tidal constituents. However, parting is aided by overtides on the eastern, mixed semidiurnal side of the strait. Bedload parting is also strongly impacted by wind-driven currents. Wind-driven currents during the trade wind season lead to the average estimates of bedload transport to be directed west, through the strait, over the 8 year model duration. As a result, east and west directed bedload parting is only active during the monsoon season when the influence of wind-driven circulation is negligible. A simulation of bedload transport using a range of sediment grain sizes indicated that sediments with a grainsize greater than ~2 mm were transported in a direction consistent with tidally driven bedload parting, as opposed to residual wind-driven flow.

Resuming earlier work and based on recently available data sources, this study explores interannual rainfall variability in Central America and underlying circulation mechanisms during 1958–2012. With the changes of circulation in the annual cycle, precipitation increases into May–June, become scarcer in July–August (JA), yet most abundant in September–October; the edge of the Atlantic subtropical high extending westward most markedly and the Pacific Intertropical Convergence Zone (ITCZ) retreating southward in JA. Interannual variations of rainfall are accompanied with circulation changes involving vertical motion over Central America. Overall, with weaker Atlantic trade winds southerly wind component over Pacific tends to be stronger and Central America rains more abundant. Regarding long-term variations from protracted dry regime 1971–1978 to protracted wet regime 2005–2012, on the Atlantic side ocean surface warmed, pressure dropped, trade winds weakened, whereas over the Pacific northward pressure gradient and winds increased. The study builds on work half a century ago and extends analysis into the most recent decades, using recent and updated circulation and raingauge data sets.

This paper focuses on the impacts of convective momentum transport (CMT) on simulations of the tropical intraseasonal oscillation (TIO) in SAMIL. Two sets of experiments are performed, which give different reality of the Madden-Julian Oscillation (MJO). The Tiedtke cumulus parameterization scheme is used for all experiments. It is found that simulations of the TIO can be influenced by CMT, and the impacts on the simulated TIO depend on the model capability in simulating the MJO. CMT tends to have large influences to the model that can simulate the eastward propagation of the MJO. CMT can further influence the long-term mean of zonal wind and its vertical shear. Zonal wind suffers from easterlies biases at low level and westerlies biases at upper level when CMT is introduced. Such easterlies biases at low level reduce the reality of the simulated tropical intraseasonal oscillation. When CMT is introduced in the model, MJO signals disappear but the model’s mean state improves. Therefore, a more appropriate way is needed to introduce CMT to the model to balance the simulated mean state and TIO signals.

The rate of coastal sea level change in the northeast Pacific (NEP) has decreased in recent decades. The relative contributions to the decreased rate from remote equatorial wind stress, local longshore wind stress, and local windstress curl are examined. Regressions of sea level onto wind stress time series and comparisons between NEP and Fremantle sea levels suggest that the decreased rate in the NEP is primarily due to oceanic adjustment to strengthened trade winds along the equatorial and coastal waveguides. When taking care to account for correlations between the various wind stress time series, the roles of longshore wind stress and local windstress curl are found to be of minor importance in comparison to equatorial forcing. The predictability of decadal sea level change rates along the NEP coastline is therefore largely determined by tropical variability. In addition, the importance of accounting for regional, wind-driven sea level variations when attempting to calculate accelerations in the long-term rate of sea level rise is demonstrated.

Several recent studies utilizing global climate models predict that the Pacific Equatorial Undercurrent (EUC) will strengthen over the twenty-first century. Here, historical changes in the tropical Pacific are investigated using the Simple Ocean Data Assimilation (SODA) reanalysis toward understanding the dynamics and mechanisms that may dictate such a change. Although SODA does not assimilate velocity observations, the seasonal-to-interannual variability of the EUC estimated by SODA corresponds well with moored observations over a ~20-yr common period. Long-term trends in SODA indicate that the EUC core velocity has increased by 16% century−1 and as much as 47% century−1 at fixed locations since the mid-1800s. Diagnosis of the zonal momentum budget in the equatorial Pacific reveals two distinct seasonal mechanisms that explain the EUC strengthening. The first is characterized by strengthening of the western Pacific trade winds and hence oceanic zonal pressure gradient during boreal spring. The second entails weakening of eastern Pacific trade winds during boreal summer, which weakens the surface current and reduces EUC deceleration through vertical friction. EUC strengthening has important ecological implications as upwelling affects the thermal and biogeochemical environment. Furthermore, given the potential large-scale influence of EUC strength and depth on the heat budget in the eastern Pacific, the seasonal strengthening of the EUC may help reconcile paradoxical observations of Walker circulation slowdown and zonal SST gradient strengthening. Such a process would represent a new dynamical “thermostat” on CO2-forced warming of the tropical Pacific Ocean, emphasizing the importance of ocean dynamics and seasonality in understanding climate change projections.

We report a documented record of a Great Frigatebird Fregata minor at Fernando de Noronha, 360 km off the coast of northeast Brazil in the equatorial Atlantic. We presume that the bird at Fernando de Noronha originated from Trindade Island, c.1,800 km to the south, since it is the species' nearest breeding site, and we hypothesise that it moved with the south-east trade winds towards the north-east Brazilian coast.

A plume of fresh water, originating from the Amazon and Orinoco Rivers, infiltrates the southeastern Caribbean. Here, some of factors underlying changes of near-surface salinity are investigated using ocean and atmosphere reanalyses that include winds, currents, sea temperature, salinity, rainfall, and river basin run-off during pre-season (April–June) and in-season (July–September) periods 1980–2016. Composite results demonstrate that increased northeasterly trade winds and an accelerated North Brazil Current feed Amazon and Orinoco River water northwestward into the Caribbean, underpinning a 0.5C warming of sea temperature and an increase in the frequency and intensity of passing hurricanes. This chain of events is partially related to the Atlantic meridional mode.

The relationship between El Nino Modoki and the East Asian-western North Pacific summer monsoon (EA-WNPSM) has been revealed to be under the influence of Indian Ocean Dipole (IOD). When a pure El Nino Modoki occurs without a positive IOD, a strong EA-WNPSM is observed with a significant anomalous low-level cyclone over the western North Pacific (WNP), excessive rainfall there and deficient Meiyu–Baiu rainfall. In contrast, when an El Nino Modoki happens simultaneously with a positive IOD, the anomalous EA-WNPSM tends to be much weaker. This difference is attributed to a positive IOD effect. The results demonstrate that a positive IOD usually leads to a strong South Asian summer monsoon heating, which further causes easterly anomalies in the western Pacific. These anomalous easterlies tend to strengthen the WNP anticyclonic vorticity leading to a weak EA-WNPSM. Therefore, a positive IOD weakens the relationship between the El Nino Modoki and the EA-WNPSM. In addition, numerical experiments verified that the strong low-level WNP cyclonic anomaly is built through the off-equatorial heating associated with the local cyclonic circulation. The anomalous WNP anticyclonic vorticity induced by a positive IOD weakens this off-equatorial heating, thus leading to a weak EA-WNPSM.

Air–sea coupling in the IntraAmerican seas (IAS; Caribbean Sea and Gulf of Mexico) is studied through analyses of observational data from satellite, reanalysis products, and in situ measurements. A strong coupling is found between the easterly trade wind −U and meridional SST gradient ∂T/∂y across a localized region of the southern-central Caribbean Sea from seasonal and interannual to decadal time scales. The ∂T/∂y anomaly is caused by a variation in the strength of coastal upwelling off the Venezuelan coast by the wind, which in turn strengthens (weakens) for stronger (weaker) ∂T/∂y. Wind speeds and seasonal fluctuations in IAS have increased in the past two decades with a transition near 1994 coinciding approximately with when the Atlantic multidecadal oscillation (AMO) turned from cold to warm phases. In particular, the seasonal swing from summer's strong to fall's weak trade wind has become larger. The ocean's upper-layer depth has also deepened, by as much as 50% on average in the eastern Gulf of Mexico. These conditions favor the shedding of eddies from the Loop Current, making it more likely to shed at a biannual frequency, as has been observed from altimetry data.

The sea surface temperature gradient (SSTG) between the southwestern Pacific Ocean (40°–20°S, 160°E–170°W) and the western Pacific warm pool (0°–16°N, 125°–165°E) in boreal spring has been identified as a new factor that controls the interannual variability of tropical cyclone (TC) frequency over the western North Pacific Ocean (WNP). This SSTG can explain 53% of the total variance of the WNP TC genesis frequency during the typhoon season for the period 1980–2011. The positive SSTG anomaly produces an anomalous cross-equatorial pressure gradient and thus anomalies in low-level southward cross-equatorial flow and tropical easterlies over the central-western Pacific. The anomalous easterlies further produce local equatorial upwelling and seasonal cooling in the central Pacific, which in turn maintains the easterly anomalies throughout the typhoon season. These dynamical/thermodynamical effects induced by the positive SSTG anomaly lead to a reduced low-level cyclonic shear, increased vertical wind shear, and weakened monsoon trough over the WNP, greatly suppressing WNP TC genesis during the typhoon season. This implies that the spring SSTG could be a good predictor for WNP TC genesis frequency.

[1] Atmospheric mixing ratios of C2H5I, CH2ClI, CH2Br2, and CHBr3 were quantified from whole air samples collected aboard the FAAM BAe 146-301 atmospheric research aircraft during flights over the tropical Atlantic Ocean (30°N to 10°S) as part of the Trade Wind Ozone Photochemistry Experiment (TROMPEX) in September 2009. Mixing ratios of C2H5I and CH2ClI increased with decreasing latitude, and concentrations of all measured halocarbons were elevated with increasing proximity to the oceanic upwelling along the coast of Mauritania. Vertical profiles highlighted the rapid photolytic degradation of these compounds within the tropical troposphere, with CH2ClI concentrations reduced by 50% at the top of the boundary layer. The spatial distributions of CH2ClI indicated an open ocean source.

Guerreiro, J.S., Ranieri, L. A., El-Robrini, M., Vila-Concejo. Seasonal changes of a dynamic macrotidal beach: Case Study of Marieta beach(Amazon Coast/Brazil) The Amazon Atlantic Coast is a very dynamic area due to the large discharge associated to a large network of rivers that include the Amazon River. Many of the beaches in this area are located within the area of influence of macrotidal range. There is a large sediment availability that creates extensive tidal flats. Waves are moderate with average offshore of 1.8m. The area has a tropical climate with two seasons, rainy and dry, and is under influence of moderate SE/NE trade winds. This paper presents topographic and hydrodynamic data from one of these beaches, Marieta Beach, and shows that while it undergoes severe erosion during the rainy season, accretion and recovery occurs during the dry season. Erosion seems to be associated to the large river discharge in the rainy season (10 3 to 10 4 m3/s−1), high water levels coupled with strong e...

International audience; The Northern Mediterranean Current is the return branch of the cyclonic circulation of the northwestern Mediterranean Sea. Because of geostrophic constraints, this warm and oligotrophic current is forced to flow westward along the continental slope of the Gulf of Lion. But, occasionally, it penetrates on the shelf and strongly impacts the local biogeochemistry and in turn the primary production. By combining in situ observations and high-resolution modelling, it is shown that intrusions on the eastern part of the gulf are mainly forced by easterly or northwesterly wind events, through physical mechanisms that are very different in nature. Easterlies induce a piling of water along the Gulf of Lion coast that drives, through geostrophy, an alongshore shelf-intruding current. This intrusive current occurs independently of the stratification and is concomitant with the wind forcing. On the other hand, intrusions due to northwesterlies only occur during stratified conditions and are related to the development of upwellings along the Gulf of Lion coasts. When the upwelling develops, a northwestward alongshore pressure force balances the Coriolis force associated with the onshore flow at depth. When the winds drop, the upwelling relaxes and the onshore flow weakens. Consequently, the Coriolis force no longer counterbalances the pressure force that ultimately dominates the momentum balance, causing the displacement of the Northern Current on the Gulf of Lion shelf approximately 1 day after the wind relaxation. This time lag between the northwesterlies decrease and the intrusions permits to anticipate possible changes in the biogeochemistry of the Gulf of Lion.

Global climate models (GCMs) predict enhanced warming and nutrient decline across the central tropical Pacific as trade winds weaken with global warming. Concurrent changes in circulation, however, have potential to mitigate these effects for equatorial islands. The implications for densely populated island nations, whose livelihoods depend on ecosystem services, are significant. A unique suite of in situ measurements coupled with state-of-the-art GCM simulations enables us to quantify the mitigation potential of the projected circulation change for three coral reef ecosystems under two future scenarios. Estimated historical trends indicate that over 100% of the large-scale warming to date has been offset locally by changes in circulation, while future simulations predict a warming mitigation effect of only 5–10% depending on the island. The pace and extent to which GCM projections overwhelm historical trends will play a key role in defining the fate of marine ecosystems and island communities across the tropical Pacific.

Queensland experiences considerable inter-annual and decadal rainfall variability, which impacts water-resource management, agriculture and infrastructure. To understand the mechanisms by which large-scale atmospheric and coupled air–sea processes drive these variations, empirical orthogonal teleconnection (EOT) analysis is applied to 1900–2010 seasonal Queensland rainfall. Fields from observations and the 20th Century Reanalysis are regressed onto the EOT timeseries to associate the EOTs with large-scale drivers. In winter, spring and summer the leading, state-wide EOTs are highly correlated with the El Nino–Southern Oscillation (ENSO); the Inter-decadal Pacific Oscillation modulates the summer ENSO teleconnection. In autumn, the leading EOT is associated with locally driven, late-season monsoon variations, while ENSO affects only tropical northern Queensland. Examining EOTs beyond the first, southeastern Queensland and the Cape York peninsula emerge as regions of coherent rainfall variability. In the southeast, rainfall anomalies respond to the strength and moisture content of onshore easterlies, controlled by Tasman Sea blocking. The summer EOT associated with onshore flow and blocking has been negative since 1970, consistent with the observed decline in rainfall along the heavily populated coast. The southeastern Queensland EOTs show considerable multi-decadal variability, which is independent of large-scale drivers. Summer rainfall in Cape York is associated with tropical-cyclone activity.

Canonical El Nino has a warming center in the eastern Pacific (EP), but in recent decades, El Nino warming center tends to occur more frequently in the central Pacific (CP). The definitions and names of this new type of El Nino, however, have been notoriously diverse, which makes it difficult to understand why the warming center shifts. Here, we show that the new type of El Nino events is characterized by: 1) the maximum warming standing and persisting in the CP and 2) the warming extending to the EP only briefly during its peak phase. For this reason, we refer to it as standing CP warming (CPW). Global warming has been blamed for the westward shift of maximum warming as well as more frequent occurrence of CPW. However, we find that since the late 1990s the standing CPW becomes a dominant mode in the Pacific; meanwhile, the epochal mean trade winds have strengthened and the equatorial thermocline slope has increased, contrary to the global warming-induced weakening trades and flattening thermocline. We propose that the recent predominance of standing CPW arises from a dramatic decadal change characterized by a grand La Nina-like background pattern and strong divergence in the CP atmospheric boundary layer. After the late 1990s, the anomalous mean CP wind divergence tends to weaken the anomalous convection and shift it westward from the underlying SST warming due to the suppressed low-level convergence feedback. This leads to a westward shift of anomalous westerly response and thus a zonally in-phase SST tendency, preventing eastward propagation of the SST anomaly. We anticipate more CPW events will occur in the coming decade provided the grand La Nina-like background state persists.