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Some bays of the subtropical west coast of South America, usually protected from the winds, have been observed as upwelling shadows (US), with anomalous high sea surface temperatures. Different arg...

Identificador de proyecto: CGL2015-72164-EXP, Upwelling is a process in which sea water from intermediate depths rises toward the surface as a response to the wind friction along the west coast of continents. Upwelled water is rich in nutrients, creating areas of paramount importance for fisheries. A long-standing hypothesis contends that upwelling might be intensified because of global warming, but due to the impediments to quantify the upwelling intensity for long periods, the scientific community still debates whether the upwelling is changing. We have used historical wind observations taken aboard ships sailing along the coast of Northwest Africa to show that there, during the last two centuries, upwelling has not increased but it has oscillated synchronically with the temperature of the North Atlantic., Departamento de Física de la Tierra y Astrofísica, Universidad Complutense, Departamento de Sistemas Físicos, Químicos y Naturales, Universidad Pablo de Olavide, IGEO, Instituto de Geociencias (CSIC, UCM)

Palmer Deep Canyon is one of the biological hotspots associated with deep bathymetric features along the Western Antarctic Peninsula. The upwelling of nutrient-rich Upper Circumpolar Deep Water to ...

25 pages, 9 figures, 3 tables.-- This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, Data from an acoustic Doppler current profiler (ADCP), a wave-gauge, a met-ocean buoy and model results provide new insights into the wave regime in a partially sheltered upwelling-driven bay, the Ría de Vigo (NW Iberia), and the adjacent continental shelf from June 2013 to August 2014. Swell on the NW-Iberian shelf comes mainly from NW directions, while wind sea comes from the NW under upwelling conditions, and from the SW under downwelling conditions. As the ria is protected from the NW and exposed to the SW, swell is almost always attenuated when entering the bay, and wave height inside the ria depends mostly on shelf wind sea variability. During the upwelling season, swell and wind sea barely enter the ria and wave heights inside the ria are small (0.21 m). During the downwelling season, shelf wind sea directly enters the ria, contributing more to the total wave height which achieves its maximum values (0.46 m). There is a cumulative action of wave and currents (wave current coupling, WCC) that is stronger during the downwelling season. The WCC entails an increase in the seabed energy which could reinforce bottom remineralization. The inter-annual variability (2009–2016) of winter wave height and WCC in the ria is associated with the combined role played by the North Atlantic Oscillation (NAO) and West Europe Pressure Anomaly (WEPA) indices. The highest waves and strongest WCC occur during the coincidence of negative NAO and positive WEPA phases and can have potentially relevant repercussions on the ecosystem services of the ria, Villacieros-Robineau and P. C. Pardo were funded by MCIN/AEI /10.13039/501100011033 through a Juan de la Cierva-Formación postdoctoral fellowship (FJCI-2017–34290) and a Personal Técnico de Apoyo grant (PTA2019-017492-I), respectively. Funding for this study was provided by the Spanish Ministry of Economy and Competitiveness project “STRAMIX” (CTM2012-35155), by the European Union FEDER (POCTEP) project “Radar On Raia” (0461_RADAR_ON_RAIA_1_E), by MCIN/ AEI /10.13039/501100011033 project “STRAUSS” (PID2019-106008RB-C21), and by the Xunta de Galicia (Grupos de Referencia Competitiva, IN607A2016/11)

Long-term temperature changes drive coastal Marine Heatwave (MHW) trends globally. Here, we provide a more comprehensive global analysis of cross-shore gradients of MHW and Sea Surface Temperatures (SST) changes using an ensemble of three satellite SST products during recent decades. Our analysis reveals depressed onshore SST trends in more than 2/3 of coastal pixels, including both eastern and western boundary current systems. These were well correlated with depressed trends of MHW exposure and severity, ranging from a −2 to −10 decrease in MHW days per decade and from a −2.5°C to −15°C.days per decade decrease in cumulative intensity. Results were consistent across all satellite products, indicating that these cross-shore gradients are a robust feature of observations. ERA reanalysis data show that neither air-sea heat fluxes nor wind driven upwelling were found to be consistent drivers. Global ocean circulation models (OFAM3 and ACCESS-OM2) have limited ability to simulate the depressed onshore trends. A heat budget analysis performed in the Chilean coast region, where models agree with observations, showed that the gradient of temperature change was controlled by an onshore increase of longwave radiative cooling, despite an increase in upwelling. This highlights the complexity of small-scale coastal ocean-atmosphere feedbacks, which coarser resolution climate models do not resolve. Here, we show that global coastal regions may act as thermal refugia for marine ecosystems from aspects of climate change and pulsative (MHW) changes. Contrary to the literature, our results suggest that driving mechanisms are region dependant, stressing the necessity to improve climate models resolution.

Author(s): Lilly, LE; Send, U; Lankhorst, M; Martz, TR; Feely, RA; Sutton, AJ; Ohman, MD | Abstract: We analyzed impacts of the 2014–2015 Pacific Warm Anomaly and 2015–2016 El Nino on physical and biogeochemical variables at two southern California Current System moorings (CCE2, nearshore upwelling off Point Conception; CCE1, offshore California Current). Nitrate and Chl-a fluorescence were l1 μM and l1 Standardized Fluorescence Unit, respectively, at CCE2 for the entire durations of the Warm Anomaly and El Nino, the two longest periods of such low values in our time series. Negative nitrate and Chl-a anomalies at CCE2 were interrupted briefly by upwelling conditions in spring 2015. Near-surface temperature anomalies appeared simultaneously at both moorings in spring 2014, indicating region-wide onset of Warm Anomaly temperatures, although sustained negative nitrate and Chl-a anomalies only occurred offshore at CCE1 during El Nino (summer 2015 to spring 2016). Warm Anomaly temperature changes were expressed more strongly in near-surface (l40 m) than subsurface (75 m) waters at both moorings, while El Nino produced comparable temperature anomalies at near-surface and subsurface depths. Nearshore Ωaragonite at 76 m showed notably fewer undersaturation events during both warm periods, suggesting an environment more conducive to calcifying organisms. Planktonic calcifying molluscs (pteropods and heteropods) increased markedly in springs 2014 and 2016 and remained modestly elevated in spring 2015. Moorings provide high-frequency measurements essential for resolving the onset timing of anomalous conditions and frequency and duration of short-term (days-to-weeks) perturbations (reduced nitrate and aragonite undersaturation events) that can affect marine organisms.

The coastal area adjacent to the Changjiang River estuary is a high-risk region for harmful algal blooms. Both Changjiang River discharge and Kuroshio intrusion influence the hydrological conditions and nutrient composition in this area which could affect the onset of diatom and dinoflagellate blooms. However, current understandings on their roles in regulating different microalgal blooms are limited. In this study, changes in stratification, water masses, and the ratio of phosphorus to nitrogen were examined during the diatom and dinoflagellate blooms in 2005 using ship cruise data. The observations showed that both the diatom and dinoflagellate blooms occurred in the continental coastal water. By enhancing the pycnocline and phosphorus stress, the Changjiang diluted water plays an important role in affecting the diatom bloom. The dinoflagellate bloom is partly supported by the supply of phosphate transported by Kuroshio intrusion and upwelling. The results of this study will help elucidate the mechanisms of large-scale harmful algal blooms in the coastal area adjacent to the Changjiang River estuary. Plain Language Summary The coastal area adjacent to the Changjiang River estuary is a high-risk region for harmful algal blooms. Intensive blooms of diatoms and dinoflagellates have been observed every year from spring to early summer. In 2005, field cruises were conducted in the East China Sea to investigate the succession process from the diatom to the dinoflagellate bloom. Based on the field investigation data, the characteristics and variation of stratification, water masses, nutrient composition, and microalgal blooms were analyzed to find out how Changjiang River discharge and Kuroshio intrusion affected the dynamics of different microalgal blooms. Four water masses were identified during the blooms, and both types of microalgal blooms were found to occur in the continental coastal water. The Changjiang River discharge was found to play an important role during the diatom bloom by enhancing the pycnocline and phosphorus stress, while the Kuroshio intrusion supplied phosphate for the development and maintenance of the large-scale dinoflagellate bloom. The results could help elucidate the mechanisms of harmful algal blooms in the coastal area adjacent to the Changjiang River estuary.

Results from an eddy-resolving ocean model simulation, an ocean reanalysis data, and reduced-gravity ocean (RGO) model simulations reach consensus in suggesting prominent decadal fluctuations of the Mindanao Current (MC) during 1960-2010. The MC was evidently enhanced during 1974-1982 and 2002-2008 and weakened during 1983-1990 and 1994-2001, with typical amplitude of similar to 2.0Sv (1Sv10(6)m(3)/s) for decadal volume transport anomaly. These variations are closely associated with the strength of the westward flowing North Equatorial Current at 130 degrees E and not evidently related with its bifurcation latitude. Experiments using a 1.5-layer RGO model are performed to understand the mechanisms. Decadal variations of the MC are primarily caused by off-equatorial wind changes in the tropical North Pacific, and winds in the latitude range of the MC (3-13 degrees N) play the dominant role. Equatorial winds between 3 degrees S and 3 degrees N generally act to attenuate the MC variability, and subtropical winds have little contribution. For zonal distribution, local wind forcing between 120 and 160 degrees E explains 67.8% of the MC decadal variability, while those in the central and eastern Pacific have weaker effects (25.0% and 7.2%, respectively). RGO model runs forced by nine wind data sets confirm the tight relationship between the MC and the western Pacific winds since the 1980s. The anomalous westerly winds under El Nino-like condition drive upwelling in the Philippine Sea through off-equatorial Ekman pumping that strengthens the MC. The relationship prior to 1980 is sensitive to the choice of wind data set, with four data sets yielding low or negative correlations. Plain Language Summary The Mindanao Current (MC) is important in supplying water to the western Pacific warm pool and the Indonesian Throughflow. The MC variabilities on seasonal and interannual time scales have been intensively investigated, whereas decadal variability of the MC was rarely explored. In this study, we used ocean model simulations and ocean reanalysis data to explore the decadal variability of the MC during 1960-2010 and the underlying causes. It is found that the MC was stronger during 1974-1982 and 2002-2008 and weaker during 1983-1990 and 1994-2001. The typical amplitude is similar to 2.0Sv (1Sv10(6)m(3)/s). We also found that wind forcing in the tropical northwest Pacific region is most important in controlling the MC transport. These variations are largely determined by the strength of the North Equatorial Current at 130 degrees E rather than the North Equatorial Current's bifurcation latitude off the Philippine coast. Subtropical wind forcing north of 23 degrees N has little contribution, whereas equatorial winds between 3 degrees S and 3 degrees N generally act to attenuate the MC variability. A tight relationship is found between the MC and the western Pacific zonal winds in decadal variability, particularly after similar to 1980. By contrast, the correlation between the MC and El Nino-Southern Oscillation is low on decadal time scale.

Physical and biogeochemical observations from an autonomous profiling Argo float in the Bay of Bengal show significant changes in upper ocean structure during the passage of tropical cyclone (TC) Hudhud (7–14 October 2014). TC Hudhud mixed water from a depth of about 50 m into the surface layers through a combination of upwelling and turbulent mixing. Mixing was extended into the depth of nutricline, the oxycline, and the subsurface‐chlorophyll‐maximum and thus had a strong impact on the biogeochemistry of the upper ocean. Before the storm, the near‐surface layer was nutrient depleted and was thus oligotrophic with the chlorophyll‐a concentration of less than 0.15 mg/m3. Storm mixing initially increased the chlorophyll by 1.4 mg/m3, increased the surface nitrate concentration to about 6.6 μM/kg, and decreased the subsurface dissolved oxygen (30–35 m) to 31% of saturation (140 μM). These conditions were favorable for phytoplankton growth resulting in an estimated increase in primary productivity averaging 1.5 g C·m−2·day−1 over 15 days. During this bloom, chlorophyll‐a increased by 3.6 mg/m3, and dissolved oxygen increased from 111% to 123% of saturation. Similar observations during TC Vardah (6–12 December 2016) showed much less mixing. Our analysis suggests that relatively small (high) translation speed and the presence of cold (warm) core eddy leads to strong (weak) oceanic response during TC Hudhud (TC Vardah). Thus, although cyclones can cause strong biogeochemical responses in the Bay of Bengal, the strength of response depends on the properties of the storm and the prevailing upper ocean structure such as the presence of mesoscale eddies

The mean trophic position (TP) of mesozooplankton largely determines how much mass and energy is available for higher trophic levels like fish. Unfortunately, the ratio of herbivores to carnivores in mesozooplankton is difficult to identify in field samples. Here, we investigated changes in the mean TP of mesozooplankton in a highly dynamic environment encompassing four distinct habitats in the southern South China Sea: the Mekong River plume, coastal upwelling region, shelf waters, and offshore oceanic waters. We used a set of variables derived from bulk and amino acid nitrogen stable isotopes from particulate organic matter and four mesozooplankton size fractions to identify changes in the nitrogen source and TP of mesozooplankton across these habitats. We found clear indications of a shift in N sources for biological production from nitrate in near‐coastal waters with shallow mixed layer depths toward an increase in diazotroph‐N inputs in oceanic waters with deep mixed layer depths where diazotrophs shaped the phytoplankton community. The N source shift was accompanied by a lengthening of the food chain (increase in the TP). This may provide further support for the connection between diazotrophy and the indirect routing of N through the marine food web. Our combined bulk and amino acid δ15N approach also allowed us to estimate the trophic enrichment (TE) of mesozooplankton across the entire regional ecosystem. When put in the context of literature values, a high TE of 5.1‰ suggested a link between ecosystem heterogeneity and the less efficient transfer of mass and energy across trophic levels., Plain Language Summary: Zooplankton are one of the central pillars of the marine food web and form an important link between the production of organic matter by phytoplankton and biomass at higher trophic levels (e.g., fish). Of particular interest are mesozooplankton (0.2–20 mm in size), which encompass a diverse assemblage of animals utilizing a range of feeding strategies, including herbivory, omnivory, and carnivory. Since mass and energy are lost with each trophic step, their prevailing feeding strategy determines the availability of mass and energy to the upper food web. The exact relationship between carnivores and herbivores in mesozooplankton has so far only been studied with complex experiments or in homogenous environments. We have now resolved zooplankton feeding relationships in a highly dynamic marine environment. Specifically, we used stable nitrogen isotopes in amino acids and bulk organic matter in combination with a habitat‐delineating method for phytoplankton to directly determine the ratio of carnivores to herbivores in zooplankton from dynamic habitats in the South China Sea. The mass and energy transfer across trophic levels is less efficient in such variable marine environments compared to stable open ocean systems. These findings represent a big step toward understanding the dynamics of planktonic food webs in general., Key Points: Trophic structure of mesozooplankton is regulated by similar environmental factors such as phytoplankton assemblages. Diazotrophy and nutrient availability correlated with enhanced mesozooplankton carnivory in a complex tropical marine ecosystem. Mass and energy transfer across trophic levels of planktonic food webs are less efficient in spatially and temporally variable ecosystems., Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/501100001659, National Foundation for Science and Technology Development (NAFOSTED) http://dx.doi.org/10.13039/100007224, National Aeronautics and Space Administration (NASA) http://dx.doi.org/10.13039/100000104, Schmidt Ocean Institute, National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001, https://doi.org/10.5061/dryad.bk3j9kdbv

Coral reef ecosystems are highly sensitive to thermal anomalies, making them vulnerable to ongoing global warming. Yet, a variety of cooling mechanisms, such as upwelling, offer some respite to cer...

Saffir-Simpson Category-4 Typhoon Malakas crossed the Kuroshio, the Western Boundary Current of the North Pacific Ocean, and moved along the path of the Kuroshio for eight days between September 12 and 20, 2016. Malakas induced a 3-4 degrees C sea surface cooling and an increase in sea surface Chlorophyll-a concentration to 0.8 mg/m(3). The total cooling area was approximately 18,000 km(2). Satellite observations show that Malakas triggered two upwelling regions associated with two mesoscale eddies, both to the northeast of Taiwan. The Regional Oceanic Modeling System (ROMS) was employed to offer insights into the dynamical mechanisms on the ocean response to a typhoon. The numerical model results reveal that a coastal upwelling event was induced by southeasterly winds blowing prior to the arrival of Malakas' outer band, and caused a surface cooling near Taiwan's northeast coast. A branch of the Taiwan Warm Current interacted with the offshore Kuroshio current to form an eddy prior to the typhoon's arrival. Malakas then facilitated the development of the near-coastal eddy. An open ocean eddy was triggered by inertial-Ekman pumping under the forcing effect of Malakas. The interaction between the southward current caused by Malakas and the northeastward flowing Kuroshio maintained these two induced mesoscale eddies. Numerical results show a near-inertial oscillation (IO) of about a 26-h period with an e-folding time scale of similar to 5 days was magnified and modulated by Malakas. The typhoon-induced oceanic phenomena were very well revealed in this combined observational and numerical modeling study. Plain Language Summary Typhoon Malakas passed through and affected the ocean to the northeast of Taiwan from September 12 to 20, 2016. Two surface cooling regions were observed by geostationary satellites after Typhoon Malakas passed by the area. The revelation of the factors responsible for inducing the oceanic surface cooling is crucial in understanding atmosphere-ocean dynamic processes and managing the local ecosystem resources. A numerical ocean model was employed in an attempt to replicate the oceanic phenomena that were observed. The model results suggest that a coastal upwelling event and an oceanic eddy were induced near the northeast coast of Taiwan prior to the arrival of the typhoon and subsequently enhanced by Malakas. An open ocean eddy was also triggered to the northeast of Taiwan by Malakas. The dynamic balance analyses of numerical model results reveal that inertialEkman pumping caused by Malakas was the critical factor in the induction of these phenomena. Eddyinduced upwelling was triggered and subsequently cooled down ocean surface temperatures. In addition, the variant typhoon wind magnified a near-inertial oscillation of about a 26-h period, in the current field, with a similar to 5-day e-folding time scale, to the northeast of Taiwan, which was imbedded into the growth and decay of the eddies.

Coastal upwelling along the southwestern coast of Sumatra is a seasonal upwelling that occurs in areas of high sea surface temperature and abundant precipitation at the southeastern edge of the Ind...

The western tropical Pacific (WTP) exhibits pronounced large-scale sea level anomalies (SLAs) during El Nino-Southern Oscillation (ENSO) events with amplitudes of similar to 0.1 m, exerting potential threats to many low-lying islands. It is found that the sea level falling in El Nino condition is evidently stronger than the rising in La Nina condition. This SLA asymmetry in the WTP associated with ENSO is investigated in this study, and the underlying dynamic processes are explored. Such asymmetry is most prominent at around 160 degrees E with the SLA response to El Nino being three times stronger than to La Nina, but it is much inconspicuous near the western boundary. Sensitivity experiments of a simplified ocean model suggest that the different structures of surface wind anomalies between El Nino and La Nina conditions are critical in generating asymmetric SLA responses of the WTP. The El Nino's westerly wind anomaly patch locates more to the east than the La Nina's easterly wind patch during the mature stage, and its upwelling effects are accumulated over a wider longitude range and cause stronger negative SLAs in the WTP. Near the western boundary, however, upwelling effects are attenuated by easterly wind anomalies during the mature stage of El Nino. Further analysis reveals that eastern Pacific-type El Nino events are more favorable for generating asymmetric SLAs in the WTP than the central Pacific-type events.

15 pages, 9 figures.-- This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited, Glider observations from the Northwestern Iberian Margin during the exceptionally strong 2010 summer upwelling season resolved the evolution of physical and biogeochemical variables during two upwelling events. Upwelling brought low‐oxygen Eastern North Atlantic Central Water from 190m depth onto the shelf up to a depth of 50 m. During the two observed periods of upwelling, a poleward jet developed over the shelf break. The persistent upwelling favorable winds maintained equatorward flow on the outer shelf for 2 months with no reversals during relaxation periods, a phenomenon not previously observed. During upwelling, near‐surface chlorophyll a concentration increased by more than 6mgm−3. Oxygen supersaturation in the near surface increased by more than 20%, 6 days after the chlorophyll a maximum., The glider deployment and investigators J. K. and K. J. H. were supported by NERC grant NE/H012532/1 Glider observations of productivity in the North Atlantic (GOPINA). Ship work by the RV Mytilus was funded through projects CAIBEX CTM2007‐66408‐C02‐01 (Plan Nacional, Spanish Ministry of Science and Education) and RAIA 0313 RAIA_1_E (INTERREG, European Union). C. R. was supported by the Natural Environment Research Council (Grant NE/N012070/1) and the Engineering and Physical Sciences Research Council, via the NEXUSS Centre of Doctoral Training in the Smart and Autonomous Observation of the Environment.

In the Caribbean Sea, mesoscale anticyclonic ocean eddies impact the local ecosystem by mixing of low salinity river outflow with the nutrient-rich waters upwelling along the Venezuelan and Colombian coast. To gain insight into the physics and the ecological impact of these anticyclones, we performed a combined hydrographic and biological survey of one Caribbean anticyclone in February 2018. We found that the anticyclone had a radius of 90 km and was surface intensified with the strongest velocities (0.72 m/s) in the upper 150 m of the water column. Below, isopycnal displacements were found down to 700 dbar. The core of the anticyclone entrained waters from the Orinoco River plume and contained slightly elevated chlorophyll concentrations compared to the surroundings. At the edge of the anticyclone we observed higher densities of flying fish but not higher densities of predators like seabirds and cetaceans. Below the surface, a strong temperature inversion (0.98 °C) was present within a barrier layer. In addition, we found thermohaline staircases that originated from double diffusion processes within Tropical Atlantic Central Water.

International audience; The West Spitsbergen Current (WSC) cools and freshens as it flows northward along the western Svalbard shelf. The cooling takes place at the ocean surface through interaction with the atmosphere and also in subsurface. We present observations with high horizontal resolution (around 2 km)from a SeaExplorer glider deployed in July 2017 for 14 days in the WSC offshore Kongsfjorden around 79°N.They document small lenses (less than 10-km diameter) of cold (less than 3.8 °C) and fresh (less than35.2 g/kg) waters in the core of the WSC, coming from the shelf and contributing to its cooling and freshening. Data show that water from the shelf cascades to the bottom of the slope and then detaches on the offshore side of the WSC core where it is baroclinically unstable. The presence of these lenses from the shelf can be related to the wind regime. Strong southerly winds cause upwelling of the warm Atlantic Water onto the shelf in winter. Weak and/or northerly winds allow modified Atlantic Water formed by mixing with cold waters on the shelf to cascade down the slope, leading to lenses of colder and fresher water protruding into the WSC. If lenses are common in the WSC, they could be contributing significantly to its cooling and freshening especially in summer when the influence of the atmosphere on the cooling of the WSC is less important.

Analyses of hydrographic observation data sets revealed that modified Circumpolar Deep Water (mCDW) tends to flood the western flank (73-78 degrees E, 67-68 degrees S) of the Four Ladies Bank (FLB) in Prydz Bay. In this study, we investigated the mechanism responsible for mCDW upwelling over the FLB based on an eddy-resolving coupled ocean-sea ice-ice shelf model in conjunction with the latest high-accuracy bathymetry. It was found that zonal step-like declines in the seabed over the FLB are crucial for the mCDW onshore upwelling, through topographic dynamic effects on the alongshore Antarctic Slope Current. In the presence of meridional cross-shelf sigma isopycnals, warm mCDW at 500-m depth in the deep sea can make its approach to the shallower continental shelf (200- to 500-m depths), characterized as a warm layer (> -1.8 degrees C) bounded by the cross-shelf sigma isopycnal surfaces of 27.5 and 27.7kg/m(3). The simulated outflow of the Prydz Bay gyre is concentrated to the eastern flank of the Prydz Channel. These results suggest that, in addition to the depressions and troughs around the Antarctic, smaller topographic features such as step-like declines in the seabed near the Antarctic Slope Current are also favorable for onshore mCDW intrusion. This study demonstrates that mCDW onshore transport around the Antarctic continental shelf might be significantly underestimated by numerical models with coarse spatial representations of the topography. Plain Language Summary Based the observational data sets, warm Circumpolar Deep Water was identified over the Four Ladies Bank in Prydz Bay, East Antarctica. The warm signals could be delivered into the ocean cavity beneath the downstream ice shelf and result in remarkable influences to the ice shelf basal melting. In order to investigate the intrusion of warm Circumpolar Deep Water, we used a numerical model to simulate the oceanic circulations in Prydz Bay. By assessing the simulated results, we found that the topographic influences of the changes in seabed on the continental shelf break jet play a dominant role in the responsible mechanism for warm water intrusion. Our findings highlighted that the improvements in the spatial resolution of the numerical model and the accuracy of the topographical representations are very useful in the investigation of warm water intrusion around the Antarctic continental shelf.

The Panama Basin serves as a laboratory to investigate abyssal water upwelling. The basin has only a single abyssal water inflow pathway through the narrow Ecuador Trench. The estimated critical inflow through the Trench reaches 0.34 ± 0.07 m s−1, resulting in an abyssal water volume inflow of 0.29 ± 0.07 Sv. The same trench carries the return flow of basin waters that starts just 200 m above the bottom and is approximately 400 m deeper than the depth of the next possible deep water exchange pathway at the Carnegie Ridge Saddle. The curvature of temperature‐salinity diagrams is used to differentiate the effect of geothermal heating on the deep Panama Basin waters that was found to reach as high as 2200 m depth, which is about 500 m above the upper boundary of the abyssal water layer.

Plain Language Summary Using in situ data, satellite observations, and model outputs, we analyzed the interannual variability in coastal upwelling intensity in the northern South China Sea. Comparing coastal upwelling observed from three cruises during the summers of 2008 and 2016, we found that coastal upwelling was stronger during 2016 compared to 2008, although the local upwelling favorable wind was stronger in 2008. The stronger near-bottom cross-shelf current and shallower thermocline in the slope resulted in stronger upwelling intensity during the summer of 2016. The topographic position index (TPI), which is defined by the sea surface temperature difference between one center cell and its neighbors, was used to quantify the interannual variability in upwelling. Stronger (weaker) upwelling intensity occurred during the summers of 2007, 2008, 2011, 2015, and 2016 (2004, 2009, 2012, and 2014) when the local wind was more favorable (less favorable) to coastal upwelling. The correlation coefficient between the area-weighted TPI and alongshore wind speed was -0.60, thereby confirming that local wind is the primary dynamical factor controlling the interannual variability in upwelling intensity. The correlation coefficient between the area-weighted TPI and the eastward boundary current transport averaged between the 75- and 100-m isobaths on the shelf was -0.42, indicating that the interannual variability in large-scale circulation in the northern South China Sea also contributes to the interannual variability in upwelling intensity. The anomalously shallow thermocline in the summer of 2016 was likely associated with the strong 2015-2016 El Nino event through planetary wave propagations.

Water properties and formation processes of Alaskan Coastal Winter Water (ACWW) over the eastern Chukchi shelf along the Alaska coast, the so-called Barrow Canyon pathway, are examined using data from moorings, atmospheric reanalysis, satellite-derived sea-ice production (SIP), and a numerical tracer experiment. Along this pathway, Pacific Winter Water (PWW) can be modified to produce ACWW through SIP accompanied by production of cold, saline polynya water in the coastal polynyas, upwelling of warm Atlantic Water (AW), and mixing processes on the shelf. Three different types of ACWW are formed: (i) a mixture of AW and PWW, (ii) a mixture of AW and polynya water, and (iii) hypersaline polynya water. The northeasterly winds, correlated with the north-south atmospheric pressure gradient between Beaufort High and Aleutian Low, are common triggers of polynya SIP episodes and AW upwelling in the Barrow Coastal Polynya (BCP). Due to the dual impact of northeasterly winds, PWW modification processes in the BCP are more complicated than what occurs elsewhere in the Chukchi Polynya. The impact of AW upwelling on the ACWW formation is most prominent in the BCP, usually centered along the coast. All types of ACWW are thought to be basically transported westward or northwestward with the Chukchi slope current and/or Beaufort Gyre and finally contribute to maintenance of the lower halocline layer especially over the Chukchi Borderland, Northwind Ridge, and southern Canada Basin. Even in the Pacific sector of the Arctic Ocean, ACWW properties are strongly influenced by both Atlantic-origin and Pacific-origin waters.

Although the supply of iron generally limits phytoplankton productivity in the Southern Ocean, substantial seasonal blooms are observed over and downstream of the Kerguelen plateau in the Indian sector of the Southern Ocean. Surprisingly, of the oceanic blooms, those associated with the deeper southern plateau last much longer (~3 months) than the northern bloom (~1‐month downstream of northern plateau). In this study, iron supply mechanisms around the southern plateau were investigated, obtaining profiles of dissolved iron (