ALBERT

Description: Numerous studies have shown the primary importance of wind stress curl in coastal upwelling dynamics. The main goal of this new analysis is to describe the QuikSCAT surface wind stress curl at various scales in the Benguela and Canary upwelling systems. The dominant spatial pattern is characterized by cyclonic curl near continental boundaries and anticyclonic curl offshore, in association with equatorward alongshore (upwelling favorable) wind stress. At a smaller scale, we demonstrate the sensitivity of the QuikSCAT wind stress curl to coastal processes related to sea surface temperature (SST) mesoscale fluctuations by presenting a linear relationship between the curl and crosswind SST gradients. Despite the spatial and temporal sensitivity of the underlying thermal coupling coefficient, a local analysis of the fraction of the curl ascribed to SST variability shows that SST is a main driver of the wind stress curl variability and magnitude over the upwelling extension zone (~100 to 300 km from the coast) in both the Canary and Benguela systems. Closer to the shore, the curl patterns derived from QuikSCAT observations are only loosely related to SST-wind interactions. As a working hypothesis, they can also be associated with the coastline geometry and orographic effects that are likely to play an important role in local cooling processes.

Description: This study investigates the structure and intensity of the surface pathways connecting to and from the central areas of the large-scale convergence regions of the eastern Pacific Ocean. Surface waters are traced with numerical Lagrangian particles transported in the velocity field of three different ocean models with horizontal resolutions that range from ¼° to 1/32°. The connections resulting from the large-scale convergent Ekman dynamics agree qualitatively but are strongly modulated by eddy variability that introduces meridional asymmetry in the amplitude of transport. Lagrangian forward-in-time integrations are used to analyze the fate of particles originating from the central regions of the convergence zones, and highlight specific outflows not yet reported for the Southeastern Pacific when using the currents at the highest resolutions (1/12° and 1/32°). The meridional scales of these outflows are comparable to the characteristic width of the fine-scale striation of mean currents.

Description: On interannual and longer time scales, dynamical and biogeochemical fluctuations in the North Pacific are dominated by two modes of variability, namely the Pacific Decadal Oscillation and the North Pacific Gyre Oscillation (NPGO). In this study the regional expression of the NPGO in the California Current System (CCS) is detailed. The statistical relationship between the NPGO index and nearshore wind variability (mostly upwelling favorable) along the U.S. West coast is strongest in the wintertime (December to March) off Central California. Most importantly, NPGO fluctuations are associated with a seasonal shift of 1–2 months in the onset of the upwelling season. Regional numerical simulations show that an early (late) onset of upwelling during the positive (negative) phase of the NPGO leads to a more (less) productive planktonic ecosystem throughout spring and summer, i.e., several months after the direct NPGO effects on the system have ceased. These results bring new light on the California ecosystem variability as observed in atypical years such as 2005 and 2007.

Description: Agulhas rings provide the principal route for ocean waters to circulate from the Indo-Pacific to the Atlantic basin. Their influence on global ocean circulation is well known, but their role in plankton transport is largely unexplored. We show that, although the coarse taxonomic structure of plankton communities is continuous across the Agulhas choke point, South Atlantic plankton diversity is altered compared with Indian Ocean source populations. Modeling and in situ sampling of a young Agulhas ring indicate that strong vertical mixing drives complex nitrogen cycling, shaping community metabolism and biogeochemical signatures as the ring and associated plankton transit westward. The peculiar local environment inside Agulhas rings may provide a selective mechanism contributing to the limited dispersal of Indian Ocean plankton populations into the Atlantic.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Villar, Emilie -- Farrant, Gregory K -- Follows, Michael -- Garczarek, Laurence -- Speich, Sabrina -- Audic, Stephane -- Bittner, Lucie -- Blanke, Bruno -- Brum, Jennifer R -- Brunet, Christophe -- Casotti, Raffaella -- Chase, Alison -- Dolan, John R -- d'Ortenzio, Fabrizio -- Gattuso, Jean-Pierre -- Grima, Nicolas -- Guidi, Lionel -- Hill, Christopher N -- Jahn, Oliver -- Jamet, Jean-Louis -- Le Goff, Herve -- Lepoivre, Cyrille -- Malviya, Shruti -- Pelletier, Eric -- Romagnan, Jean-Baptiste -- Roux, Simon -- Santini, Sebastien -- Scalco, Eleonora -- Schwenck, Sarah M -- Tanaka, Atsuko -- Testor, Pierre -- Vannier, Thomas -- Vincent, Flora -- Zingone, Adriana -- Dimier, Celine -- Picheral, Marc -- Searson, Sarah -- Kandels-Lewis, Stefanie -- Tara Oceans Coordinators -- Acinas, Silvia G -- Bork, Peer -- Boss, Emmanuel -- de Vargas, Colomban -- Gorsky, Gabriel -- Ogata, Hiroyuki -- Pesant, Stephane -- Sullivan, Matthew B -- Sunagawa, Shinichi -- Wincker, Patrick -- Karsenti, Eric -- Bowler, Chris -- Not, Fabrice -- Hingamp, Pascal -- Iudicone, Daniele -- New York, N.Y. -- Science. 2015 May 22;348(6237):1261447. doi: 10.1126/science.1261447.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Aix Marseille Universite, CNRS, IGS UMR 7256, 13288 Marseille, France. villar@igs.cnrs-mrs.fr not@sb-roscoff.fr hingamp@igs.cnrs-mrs.fr iudicone@szn.it karsenti@embl.de cbowler@biologie.ens.fr. ; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. Sorbonne Universites, Universite Pierre et Marie Curie UPMC, Universite Paris 06, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. ; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA. ; Laboratoire de Physique des Oceans (LPO) UMR 6523 CNRS-Ifremer-IRD-UBO, Plouzane, France. Department of Geosciences, Laboratoire de Meteorologie Dynamique (LMD) UMR 8539, Ecole Normale Superieure, 24 Rue Lhomond, 75231 Paris Cedex 05, France. ; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. Sorbonne Universites, Universite Pierre et Marie Curie UPMC, Universite Paris 06, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. Ecole Normale Superieure, Institut de Biologie de l'ENS (IBENS), and Inserm U1024, and CNRS UMR 8197, F-75005 Paris, France. ; Laboratoire de Physique des Oceans (LPO) UMR 6523 CNRS-Ifremer-IRD-UBO, Plouzane, France. ; Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721, USA. ; Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy. ; School of Marine Sciences, University of Maine, Orono, ME, USA. ; Sorbonne Universites, UPMC Universite Paris 06, Observatoire Oceanologique, F-06230 Villefranche-sur-Mer, France. INSU-CNRS, UMR 7093, LOV, Observatoire Oceanologique, F-06230 Villefranche-sur-Mer, France. ; Universite de Toulon, Laboratoire PROTEE-EBMA E.A. 3819, BP 20132, 83957 La Garde Cedex, France. ; CNRS, UMR 7159, Laboratoire d'Oceanographie et du Climat LOCEAN, 4 Place Jussieu, 75005 Paris, France. ; Aix Marseille Universite, CNRS, IGS UMR 7256, 13288 Marseille, France. ; Ecole Normale Superieure, Institut de Biologie de l'ENS (IBENS), and Inserm U1024, and CNRS UMR 8197, F-75005 Paris, France. ; Commissariat a l'Energie Atomique et aux Energies Alternatives (CEA), Institut de Genomique, Genoscope, 2 Rue Gaston Cremieux, 91057 Evry, France. CNRS, UMR 8030, CP5706, Evry, France. Universite d'Evry, UMR 8030, CP5706, Evry, France. ; Structural and Computational Biology, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. Directors' Research, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. ; Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM), CSIC, Passeig Maritim de la Barceloneta, 37-49, Barcelona E08003, Spain. ; Structural and Computational Biology, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. Max-Delbruck-Centre for Molecular Medicine, 13092 Berlin, Germany. ; PANGAEA, Data Publisher for Earth and Environmental Science, University of Bremen, Bremen, Germany. MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany. ; Structural and Computational Biology, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. ; Ecole Normale Superieure, Institut de Biologie de l'ENS (IBENS), and Inserm U1024, and CNRS UMR 8197, F-75005 Paris, France. Directors' Research, European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany. villar@igs.cnrs-mrs.fr not@sb-roscoff.fr hingamp@igs.cnrs-mrs.fr iudicone@szn.it karsenti@embl.de cbowler@biologie.ens.fr. ; Ecole Normale Superieure, Institut de Biologie de l'ENS (IBENS), and Inserm U1024, and CNRS UMR 8197, F-75005 Paris, France. villar@igs.cnrs-mrs.fr not@sb-roscoff.fr hingamp@igs.cnrs-mrs.fr iudicone@szn.it karsenti@embl.de cbowler@biologie.ens.fr. ; CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. Sorbonne Universites, Universite Pierre et Marie Curie UPMC, Universite Paris 06, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, 29680 Roscoff, France. villar@igs.cnrs-mrs.fr not@sb-roscoff.fr hingamp@igs.cnrs-mrs.fr iudicone@szn.it karsenti@embl.de cbowler@biologie.ens.fr. ; Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy. villar@igs.cnrs-mrs.fr not@sb-roscoff.fr hingamp@igs.cnrs-mrs.fr iudicone@szn.it karsenti@embl.de cbowler@biologie.ens.fr.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25999514" target="_blank"〉PubMed〈/a〉

Description: The climatological vision of the circulation within the Coral Sea is today well established with the westward circulation of two main jets, the North Caledonian Jet (NCJ) and the North Vanuatu Jet (NVJ) as a consequence of the separation of the South Equatorial Current (SEC) on the islands of New Caledonia, Vanuatu and Fiji. Each jet has its own dynamic and transports different water masses across the Coral Sea. The influence of mesoscale activity on mean flow and on water mass exchanges is not yet fully explored in this region of intense activity. Our study relies on the analysis of in situ , satellite and numerical data. Indeed we first use in situ data from the Bifurcation cruise and from an Argo float, jointly with satellite-derived velocities, to study the eddy influence on the Coral Sea dynamics. We identify an anticyclonic eddy as participating in the transport of NVJ-like water masses into the theoretical pathway of NCJ waters. This transfer from the NVJ to the NCJ is confirmed over the long-term by a Lagrangian analysis. In particular, this numerical analysis shows that anticyclonic eddies can contribute up to 70% to 90% of the overall eddy transfer between those seemingly independent jets. Finally, transports calculated using S-ADCP measurements (0-500 m) show an eddy-induced sensitivity that can reach up to 15 Sv, i.e, the order of the transport of the jets. This article is protected by copyright. All rights reserved.

Description: We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at ¼° resolution and refreshed daily over the 1985-2013 period. Results confirm and document the five known sites of surface convergence at the scale of individual oceanic basins, but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea and the southwest Pacific Ocean. This “super-convergent” pathway at the ocean surface is robust and permanent over a distance longer than 8000 km. The currents variability is crucial to sustain this pathway.

Description: Satellite scatterometers provide continuously valuable surface wind speed and direction estimates over the global ocean on a regular grid both in space and time. The Level 3 data derived from the Advanced Scatterometer (ASCAT), available at 1/4° spatial resolution (hereafter AS25), and Quick Scatterometer (QuikSCAT), available on 1/2° and 1/4° horizontal grids (QS50 and QS25 respectively), are studied at regional scales in both the Benguela and Canary upwelling systems. They are compared to the European Center for Medium-Range Weather Forecast surface wind analysis, with insight into their intrinsic and actual spatial resolutions. In the coastal band, the finest spatial patterns are found in the QS25 winds and are O(75 km). This demonstrates the sensitivity of the high-resolution satellite-derived winds to coastal processes related to sea surface temperature (SST) perturbations and land-sea transition. Next, short-lived upwelling episodes (SUEs) calculated from SST anomalies are defined consistently with the QS25 actual resolution. These cold events refer to local, short-lived perturbations that add to seasonal upwelling variability. We characterize concomitant atmospheric synoptic conditions for SUEs identified at chosen latitudes and highlight two subregions in both upwelling systems, with contrasted patterns for the alongshore wind stress component and curl. The complexity of the latter patterns is closely linked to local, short-term SST variability. Closer to the shore, numerical sensitivity experiments show that the imbalance between Ekman transport and Ekman pumping has an impact on ocean dynamics: wind reduction in the coastal QS25 forcing, partially induced by orography, tends to reduce coastal SST cooling.

Description: We study the dispersion and convergence of marine floating material by surface currents from a model reanalysis that represents explicitly mesoscale eddy variability. Lagrangian experiments about the long-term evolution (29 years) of an initially homogeneous concentration of particles are performed at global scale with horizontal current at one fourth degree resolution and refreshed daily over the 1985–2013 period. Results not only confirm and document the five known sites of surface convergence at the scale of individual oceanic basins but also reveal a convergent pathway connecting the South Indian subtropical region with the convergence zone of the South Pacific through the Great Australian Bight, the Tasman Sea, and the southwest Pacific Ocean. This “superconvergent” pathway at the ocean surface is robust and permanent over a distance longer than 8,000 km. The current variability is crucial to sustain this pathway. ©2018. American Geophysical Union. All Rights Reserved.

Description: The effect of salinity on the formation of the barrier layer (BL) in the southeastern Arabian Sea (SEAS) is investigated using an ocean general circulation model. In accordance with previous studies, the runoff distribution and the India–Sri Lanka passage have a strong impact on the realism of the salinity simulated in the area at seasonal time scales. The model simulates a BL pattern in fairly good agreement with available observations. Eulerian and Lagrangian approaches show that the BL is formed by two complementary processes, the arrival of low-salinity surface waters that are cooled en route to the SEAS and downwelling of waters mostly local to the SEAS in the subsurface layers. The surface waters are partly of Bay of Bengal origin and are partly from the SEAS, but are cooled east and south of Sri Lanka in the model. That the downwelled subsurface waters are warm and are not cooled leads to temperature inversions in the BL. The main forcing for this appears to be remotely forced planetary waves.