Links between interannual climate variability and marine ecosystems in the Tropical Atlantic

The interannual climate variability in the Tropical Atlantic is mainly controlled by two air-sea coupled modes denoted as Meridional Mode (MM) and Equatorial Mode (EM). The MM, peaking in boreal spring, is characterized by an anomalous Sea Surface Temperature (SST) interhemispheric gradient associated with anomalous surface cross-equatorial winds blowing to the warmer hemisphere.&#160; On the other hand, the positive phase of the EM exhibits an anomalous warming in the equatorial band and along the African coast, related to a weakening of the climatological trade winds. Both interannual modes illustrate significant SST and surface wind changes in the eastern boundary upwelling systems (EBUS) of the tropical Atlantic: the Senegal-Mauritanian and Angola-Benguela. The EBUS are characterized by wind-induced coastal upwelling of deep cold waters rich in nutrients supporting high primary productivity and an abundance of food resources. Hence, the physical or climate characteristics associated with the MM and EM may have a potential effect on marine organisms and ecosystems. The goal of this study is to understand the links between the main modes of tropical Atlantic variability and biogeochemical (BGC) variables such as oxygen, net primary production and ph. These are known to be the main drivers for marine ecosystems. Firstly we study the influence of MM and AM on the EBUS and how these links are represented by the coupled ESM CNRM-ESM2.1 against observations. Second, we use the ESM to investigate the links between the SST anomalies associated to MM and EM and the main BGC stressors mentioned above. For this purpose, a set of numerical experiments performed with CMIP6 climate models are used. This work is supported by the H2020 TRIATLAS project, whose main goal is to understand and evaluate the future evolution of living marine resources in the Atlantic Ocean.

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Patterns of interannual climate variability in large marine ecosystems

Journal of Marine Systems ◽

10.1016/j.jmarsys.2014.03.004 ◽

2014 ◽

Vol 134 ◽

pp. 57-68 ◽

Cited By ~ 10

Author(s):

Helena Cachanhuk Soares ◽

Douglas Francisco Marcolino Gherardi ◽

Luciano Ponzi Pezzi ◽

Mary Toshie Kayano ◽

Eduardo Tavares Paes

Keyword(s):

Climate Variability ◽

Marine Ecosystems ◽

Large Marine Ecosystems ◽

Interannual Climate Variability

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Interaction between the Boreal Spring and Summer Tropical Atlantic Interannual Variability Modes

10.5194/egusphere-egu2020-7291 ◽

2020 ◽

Author(s):

Marta Martín-Rey ◽

Jose Luis Pelegrí ◽

Emilia Sánchez-Gómez ◽

Christophe Cassou

Keyword(s):

Climate Models ◽

Ocean Dynamics ◽

Tropical Atlantic ◽

Coupled Modes ◽

Boreal Spring ◽

The North ◽

Tropical Atlantic Variability ◽

Coupled Climate Models ◽

Sea Surface Temperature Anomalies

Traditionally, the interannual Tropical Atlantic variability (TAV) is thought to be governed by two air-sea coupled modes denoted as Meridional Mode (MM) and Equatorial Mode (EM), peaking in boreal spring and summer respectively. Several studies have proposed a possible connection between the MM and EM, but without reaching a consensus about its frequency, type and associated mechanisms. Remarkably, recent findings brought to light decadal changes in the structure, intensity and teleconnections of the EM along the observational record. In particular, new overlooked equatorial modes called &#8216;non-canonical EM&#8217; and &#8216;Horse-Shoe mode&#8217; have been reported, which exhibit significant sea surface temperature anomalies in the north tropical Atlantic region. This gives robustness to the connection between the boreal spring and summer interannual modes.Here, using observational and CMIP6 model datasets, we demonstrate the existence of distinct interannual modes in the tropical Atlantic basin along the record. Furthermore, the emergence of these modes is not stationary on time and varies from some decades to the others.&#160; In this study, using observations and coupled climate models we explore the connection between the MM and EM to generate the diverse of tropical Atlantic variability reported in previous works. Moreover, the air-sea mechanisms and ocean dynamics involved in the evolution of these modes and the role of the mean state in the connection between them is assessed.

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The effect of coastal upwelling on the sea-breeze circulation at Cabo Frio, Brazil: a numerical experiment

Annales Geophysicae ◽

10.1007/s00585-998-0866-3 ◽

1998 ◽

Vol 16 (7) ◽

pp. 866-871 ◽

Cited By ~ 34

Author(s):

S. H. Franchito ◽

V. B. Rao ◽

J. L. Stech ◽

J. A. Lorenzzetti

Keyword(s):

Coastal Upwelling ◽

Surface Wind ◽

Three Dimensional ◽

Sea Breeze ◽

Atmospheric Model ◽

Ocean Model ◽

Breeze Circulation ◽

Mesoscale Meteorology ◽

Forcing Function ◽

Cabo Frio

Abstract. The effect of coastal upwelling on sea-breeze circulation in Cabo Frio (Brazil) and the feedback of sea-breeze on the upwelling signal in this region are investigated. In order to study the effect of coastal upwelling on sea-breeze a non-linear, three-dimensional, primitive equation atmospheric model is employed. The model considers only dry air and employs boundary layer formulation. The surface temperature is determined by a forcing function applied to the Earth's surface. In order to investigate the seasonal variations of the circulation, numerical experiments considering three-month means are conducted: January-February-March (JFM), April-May-June (AMJ), July-August-September (JAS) and October-November-December (OND). The model results show that the sea-breeze is most intense near the coast at all the seasons. The sea-breeze is stronger in OND and JFM, when the upwelling occurs, and weaker in AMJ and JAS, when there is no upwelling. Numerical simulations also show that when the upwelling occurs the sea-breeze develops and attains maximum intensity earlier than when it does not occur. Observations show a similar behavior. In order to verify the effect of the sea-breeze surface wind on the upwelling, a two-layer finite element ocean model is also implemented. The results of simulations using this model, forced by the wind generated in the sea-breeze model, show that the sea-breeze effectively enhances the upwelling signal.Key words. Meteorology and atmospheric dynamics (mesoscale meteorology; ocean-atmosphere interactions) · Oceanography (numerical modeling)

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Cumulus over the Tibetan Plateau in the Summer Based on CloudSat–CALIPSO Data

Journal of Climate ◽

10.1175/jcli-d-15-0492.1 ◽

2016 ◽

Vol 29 (3) ◽

pp. 1219-1230 ◽

Cited By ~ 18

Author(s):

Yunying Li ◽

Minghua Zhang

Keyword(s):

Tibetan Plateau ◽

Climate Models ◽

Surface Wind ◽

Lower Atmosphere ◽

The Tibetan Plateau ◽

Shallow Convection ◽

Free Atmosphere ◽

Northern Summer ◽

Static Energy ◽

Fine Resolution

Abstract Cumulus (Cu) can transport heat and water vapor from the boundary layer to the free atmosphere, leading to the redistribution of heat and moist energy in the lower atmosphere. This paper uses the fine-resolution CloudSat–CALIPSO product to characterize Cu over the Tibetan Plateau (TP). It is found that Cu is one of the dominant cloud types over the TP in the northern summer. The Cu event frequency, defined as Cu occurring within 50-km segments, is 54% over the TP in the summer, which is much larger over the TP than in its surrounding regions. The surface wind vector converging at the central TP and the topographic forcing provide the necessary moisture and dynamical lifting of convection over the TP. The structure of the atmospheric moist static energy shows that the thermodynamical environment over the northern TP can be characterized as having weak instability, a shallow layer of instability, and lower altitudes for the level of free convection. The diurnal variation of Cu with frequency peaks during the daytime confirms the surface thermodynamic control on Cu formation over the TP. This study offers insights into how surface heat is transported to the free troposphere over the TP and provides an observational test of climate models in simulating shallow convection over the TP.

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Evaluating the Uncertainty Induced by the Virtual Salt Flux Assumption in Climate Simulations and Future Projections

Journal of Climate ◽

10.1175/2009jcli3084.1 ◽

2010 ◽

Vol 23 (1) ◽

pp. 80-96 ◽

Cited By ~ 28

Author(s):

Jianjun Yin ◽

Ronald J. Stouffer ◽

Michael J. Spelman ◽

Stephen M. Griffies

Keyword(s):

Climate Models ◽

Climate Model ◽

Ocean Model ◽

Salt Flux ◽

Freshwater Flux ◽

Unexpected Result ◽

Geophysical Fluid Dynamics Laboratory ◽

External Forcing ◽

Future Evolution ◽

Near Term

Abstract The unphysical virtual salt flux (VSF) formulation widely used in the ocean component of climate models has the potential to cause systematic and significant biases in modeling the climate system and projecting its future evolution. Here a freshwater flux (FWF) and a virtual salt flux version of the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 (GFDL CM2.1) are used to evaluate and quantify the uncertainties induced by the VSF formulation. Both unforced and forced runs with the two model versions are performed and compared in detail. It is found that the differences between the two versions are generally small or statistically insignificant in the unforced control runs and in the runs with a small external forcing. In response to a large external forcing, however, some biases in the VSF version become significant, especially the responses of regional salinity and global sea level. However, many fundamental aspects of the responses differ only quantitatively between the two versions. An unexpected result is the distinctly different ENSO responses. Under a strong external freshwater forcing, the great enhancement of the ENSO variability simulated by the FWF version does not occur in the VSF version and is caused by the overexpansion of the top model layer. In summary, the principle assumption behind using virtual salt flux is not seriously violated and the VSF model has the ability to simulate the current climate and project near-term climate evolution. For some special studies such as a large hosing experiment, however, both the VSF formulation and the use of the FWF in the geopotential coordinate ocean model could have some deficiencies and one should be cautious to avoid them.

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SEASONAL PATTERN OF WIND INDUCED UPWELLING OVER JAVA-BALI SEA WATERS AND SURROUNDING AREA

International Journal of Remote Sensing and Earth Sciences (IJReSES) ◽

10.30536/j.ijreses.2008.v5.a1228 ◽

2010 ◽

Vol 5 (1) ◽

Author(s):

Siswanto ◽

Suratno

Keyword(s):

Wind Stress ◽

Coastal Upwelling ◽

Sea Water ◽

Mixed Layer Depth ◽

Surface Wind ◽

Ekman Transport ◽

Monsoon Circulation ◽

Wide Field ◽

Surrounding Area ◽

Noaa Avhrr

The influence of monsoonal wind to coastal upwelling mechanism which is generated by Ekman transport was studied here by analyzing wind stress curl (WSC) distribution over Java-Bali Sea waters and its surrounding area. Surface wind data were used as input data to calculate curl of wind stress in barotropic model. Confirmation with Corioli effect in the Southern Hemisphere, it could be known that negative curl value has relation with vertical motion of sea water as resulted by Ekman transport. Result of analysis showed that negative curl near coast over Java Sea which is stretching to Lombok Sea occurred in December to April when westerly wind of the North West Monsoon actives. It can be guidance and related with season of coastal upwelling in the region. Reversal condition, the occurrance of coastal upwelling in the south coast of JAva island related with the negative value of WSC that occurs since easterlies wind take place in May to August as a part of South East Monsoon episode. Generally, upwelling occurrance in the field of study is a response to the Monsoon circulation. This study with related data such as sea surface temperature, chlorophyll concetration and mixed layer depth that derived from satellite imaging data National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer (NOAA-AVHRR), Aqua/Modis and sea viewing Wide Field-of-view Sensor(Sea WiFS) shows as magnificent confirmation pattern. So applying WSC to recoqnize upwelling zone is alternatively way as climatic approach to maps potential fertilizing of sea water in maritime-continent Indonesia. Key words: coastal upwelling, Ekman transport, Java-Bali Sea, Monsoon circulation, upwelling.

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An Empirical Model for Surface Wind Stress Response to SST Forcing Induced by Tropical Instability Waves (TIWs) in the Eastern Equatorial Pacific

Monthly Weather Review ◽

10.1175/2008mwr2712.1 ◽

2009 ◽

Vol 137 (6) ◽

pp. 2021-2046 ◽

Cited By ~ 15

Author(s):

Rong-Hua Zhang ◽

Antonio J. Busalacchi

Keyword(s):

Wind Stress ◽

Empirical Model ◽

Stress Responses ◽

Large Scale ◽

Climate Models ◽

Surface Wind ◽

Microwave Remote Sensing ◽

Instability Waves ◽

Tropical Instability Waves ◽

Sst Forcing

Abstract High-resolution space-based observations reveal significant two-way air–sea interactions associated with tropical instability waves (TIWs); their roles in budgets of heat, salt, momentum, and biogeochemical fields in the tropical oceans have been recently demonstrated. However, dynamical model-based simulations of the atmospheric response to TIW-induced sea surface temperature (SSTTIW) perturbations remain a great challenge because of the limitation in spatial resolution and realistic representations of the related processes in the atmospheric planetary boundary layer (PBL) and their interactions with the overlying free troposphere. Using microwave remote sensing data, an empirical model is derived to depict wind stress perturbations induced by TIW-related SST forcing in the eastern tropical Pacific Ocean. Wind data are based on space–time blending of Quick Scatterometer (QuikSCAT) Direction Interval Retrieval with Thresholded Nudging (DIRTH) satellite observations and NCEP analysis fields; SST data are from the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). These daily data are first subject to a spatial filter of 12° moving average in the zonal direction to extract TIW-related wind stress (τTIW) and SSTTIW perturbations. A combined singular value decomposition (SVD) analysis is then applied to these zonal high-pass-filtered τTIW and SSTTIW fields. It is demonstrated that the SVD-based analysis technique can effectively extract TIW-induced covariability patterns in the atmosphere and ocean, acting as a filter by passing wind signals that are directly related with the SSTTIW forcing over the TIW active regions. As a result, the empirical model can well represent TIW-induced wind stress responses as revealed directly from satellite measurements (e.g., the structure and phase), but the amplitude can be underestimated significantly. Validation and sensitivity experiments are performed to illustrate the robustness of the empirical τTIW model. Further applications are discussed for taking into account the TIW-induced wind responses and feedback effects that are missing in large-scale climate models and atmospheric reanalysis data, as well as for uncoupled ocean and coupled mesoscale and large-scale air–sea modeling studies.

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