scholarly journals Divergent trajectories of ocean warming and acidification

2021 ◽  
Author(s):  
Eric A Mortenson ◽  
Andrew Lenton ◽  
Elizabeth H. Shadwick ◽  
Thomas W. Trull ◽  
Matthew A. Chamberlain ◽  
...  
Keyword(s):  
Marine Ecosystem ◽  
Ocean Model ◽  
Ocean Warming ◽  
Sea Surface ◽  
Anthropogenic Heat ◽  
Regional Variability ◽  
Regional Patterns ◽  
Emission Pathway ◽  
Surface Warming ◽  
The North

Abstract The ocean provides a major sink for anthropogenic heat and carbon. This sink results in ocean changes through the dual stressors of warming and acidification which can negatively impact the health of the marine ecosystem. Projecting the ocean’s future uptake is essential to understand and adapt to further climate change and its impact on the ocean. Historical ocean uptake of heat and CO2 are tightly correlated, but here we show the trajectories diverge over the 21st century. This divergence occurs regionally, increasing over time, resulting from the unique combination of physical and chemical drivers. We explored this relationship using a high-resolution ocean model and a ‘business as usual’ CO2 emission pathway, and demonstrate that the regional variability in the carbon-to-heat uptake ratios is more pronounced than for the subsequent carbon-to-heat storage (change in inventory) ratios, with a range of a factor of 30 (6) in heat-to-carbon uptake (storage) ratios among the defined regions. The regional differences in heat and carbon trajectories result in coherent regional patterns for sea surface warming and acidification by the end of this century. Relative to the mean global change (MGC) at the sea surface of 2.55°C warming and a decrease of 0.32 in pH, the North Pacific will exceed the MGC for both warming and acidification, the Southern Ocean for acidification only, and the tropics and midlatitude northern hemisphere will exceed MGC only for warming. Regionally, mapping the ocean warming and acidification informs where the marine environment will experience larger changes in one or both. Globally, the projected ocean uptake of anthropogenic heat and carbon informs the degree to which the ocean can continue to serve as a sink for both into the future.

scholarly journals On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ndague Diogoul ◽  
Patrice Brehmer ◽  
Hervé Demarcq ◽  
Salaheddine El Ayoubi ◽  
Abou Thiam ◽  
...  
Keyword(s):  
Multiple Stressors ◽  
Marine Ecosystem ◽  
Trophic Levels ◽  
Sea Surface ◽  
Relative Index ◽  
Upwelling System ◽  
The North ◽  
Latitudinal Shift ◽  
Large Marine Ecosystem ◽  
North And South

AbstractThe resistance of an east border upwelling system was investigated using relative index of marine pelagic biomass estimates under a changing environment spanning 20-years in the strongly exploited southern Canary Current Large marine Ecosystem (sCCLME). We divided the sCCLME in two parts (north and south of Cap Blanc), based on oceanographic regimes. We delineated two size-based groups (“plankton” and “pelagic fish”) corresponding to lower and higher trophic levels, respectively. Over the 20-year period, all spatial remote sensing environmental variables increased significantly, except in the area south of Cap Blanc where sea surface Chlorophyll-a concentrations declined and the upwelling favorable wind was stable. Relative index of marine pelagic abundance was higher in the south area compared to the north area of Cap Blanc. No significant latitudinal shift to the mass center was detected, regardless of trophic level. Relative pelagic abundance did not change, suggesting sCCLME pelagic organisms were able to adapt to changing environmental conditions. Despite strong annual variability and the presence of major stressors (overfishing, climate change), the marine pelagic ressources, mainly fish and plankton remained relatively stable over the two decades, advancing our understanding on the resistance of this east border upwelling system.

scholarly journals Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic meridional overturning circulation

Ocean Science ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 881-891 ◽  
Author(s):  
S.-E. Brunnabend ◽  
H. A. Dijkstra ◽  
M. A. Kliphuis ◽  
B. van Werkhoven ◽  
H. E. Bal ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atlantic Meridional Overturning Circulation ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Sea Level Changes ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning

Abstract. As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH) changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic meridional overturning circulation (AMOC) are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR) strongly eddying version and a low-resolution (LR) version in which the effect of eddies is parameterised. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.

scholarly journals The Use of MTM-SVD Technique to Explore the Joint Spatiotemporal Modes of Wind and Sea Surface Variability in the North Indian Ocean during 1993–2005

2009 ◽  
Vol 2009 ◽  
pp. 1-11 ◽  
Author(s):  
Thaned Rojsiraphisal ◽  
Balaji Rajagopalan ◽  
Lakshmi Kantha
Keyword(s):  
Indian Ocean ◽  
Ocean Model ◽  
North Indian Ocean ◽  
Sea Surface ◽  
Ocean Climate ◽  
Modes Of Variability ◽  
The North ◽  
Monsoon Variability ◽  
Value Decomposition ◽  
Surface Variability

Sea surface height (SSH) and sea surface temperature (SST) in the North Indian Ocean are affected predominantly by the seasonally reversing monsoons and in turn feed back on monsoon variability. In this study, a set of data generated from a data-assimilative ocean model is used to examine coherent spatiotemporal modes of variability of winds and surface parameters using a frequency domain technique, Multiple Taper Method with Singular Value Decomposition (MTM-SVD). The analysis shows significant variability at annual and semiannual frequencies in these fields individually and jointly. The joint variability of winds and SSH is significant at interannual (2-3 years) timescale related to the ENSO mode—with a “/dipole/” like spatial pattern. Joint variability with SST showed similar but somewhat weaker behavior. Winds appear to be the driver of variability in both SSH and SST at these frequency bands. This offers prospects for long-lead projections of the North Indian Ocean climate.

scholarly journals Impact of data assimilation of physical variables on the spring bloom from TOPAZ operational runs in the North Atlantic

Ocean Science ◽  
2009 ◽  
Vol 5 (4) ◽  
pp. 635-647 ◽  
Author(s):  
A. Samuelsen ◽  
L. Bertino ◽  
C. Hansen
Keyword(s):  
Data Assimilation ◽  
North Atlantic ◽  
Spring Bloom ◽  
Ecosystem Model ◽  
Ocean Model ◽  
Sea Surface ◽  
The Arctic ◽  
The North ◽  
The North Atlantic ◽  
The Impact

Abstract. A reanalysis of the North Atlantic spring bloom in 2007 was produced using the real-time analysis from the TOPAZ North Atlantic and Arctic forecasting system. The TOPAZ system uses a hybrid coordinate general circulation ocean model and assimilates physical observations: sea surface anomalies, sea surface temperatures, and sea-ice concentrations using the Ensemble Kalman Filter. This ocean model was coupled to an ecosystem model, NORWECOM (Norwegian Ecological Model System), and the TOPAZ-NORWECOM coupled model was run throughout the spring and summer of 2007. The ecosystem model was run online, restarting from analyzed physical fields (result after data assimilation) every 7 days. Biological variables were not assimilated in the model. The main purpose of the study was to investigate the impact of physical data assimilation on the ecosystem model. This was determined by comparing the results to those from a model without assimilation of physical data. The regions of focus are the North Atlantic and the Arctic Ocean. Assimilation of physical variables does not affect the results from the ecosystem model significantly. The differences between the weekly mean values of chlorophyll are normally within 5–10% during the summer months, and the maximum difference of ~20% occurs in the Arctic, also during summer. Special attention was paid to the nutrient input from the North Atlantic to the Nordic Seas and the impact of ice-assimilation on the ecosystem. The ice-assimilation increased the phytoplankton concentration: because there was less ice in the assimilation run, this increased both the mixing of nutrients during winter and the area where production could occur during summer. The forecast was also compared to remotely sensed chlorophyll, climatological nutrients, and in-situ data. The results show that the model reproduces a realistic annual cycle, but the chlorophyll concentrations tend to be between 0.1 and 1.0 mg chla/m3 too low during winter and spring and 1–2 mg chla/m3 too high during summer. Surface nutrients on the other hand are generally lower than the climatology throughout the year.

Why Does Global Warming Weaken the Gulf Stream but Intensify the Kuroshio?

2019 ◽  
Vol 32 (21) ◽  
pp. 7437-7451 ◽  
Author(s):  
Changlin Chen ◽  
Guihua Wang ◽  
Shang-Ping Xie ◽  
Wei Liu
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
North Atlantic ◽  
North Pacific ◽  
Gulf Stream ◽  
Sea Surface ◽  
Surface Warming ◽  
The North ◽  
The Kuroshio ◽  
The North Pacific

ABSTRACT The Kuroshio and Gulf Stream, the subtropical western boundary currents of the North Pacific and North Atlantic, play important roles in meridional heat transport and ocean–atmosphere interaction processes. Using a multimodel ensemble of future projections, we show that a warmer climate intensifies the upper-layer Kuroshio, in contrast to the previously documented slowdown of the Gulf Stream. Our ocean general circulation model experiments show that the sea surface warming, not the wind change, is the dominant forcing that causes the upper-layer Kuroshio to intensify in a warming climate. Forced by the sea surface warming, ocean subduction and advection processes result in a stronger warming to the east of the Kuroshio than to the west, which increases the isopycnal slope across the Kuroshio, and hence intensifies the Kuroshio. In the North Atlantic, the Gulf Stream slows down as part of the Atlantic meridional overturning circulation (AMOC) response to surface salinity decrease in the high latitudes under global warming. The distinct responses of the Gulf Stream and Kuroshio to climate warming are accompanied by different regional patterns of sea level rise. While the sea level rise accelerates along the northeastern U.S. coast as the AMOC weakens, it remains close to the global mean rate along the East Asian coast as the intensifying Kuroshio is associated with the enhanced sea level rise offshore in the North Pacific subtropical gyre.

scholarly journals Effect of Atlantic Meridional Overturning Circulation Changes on Tropical Atlantic Sea Surface Temperature Variability: A 2½-Layer Reduced-Gravity Ocean Model Study

2010 ◽  
Vol 23 (2) ◽  
pp. 312-332 ◽  
Author(s):  
Caihong Wen ◽  
Ping Chang ◽  
Ramalingam Saravanan
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Atlantic Meridional Overturning Circulation ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Subsurface Temperature ◽  
The North ◽  
Meridional Overturning

Abstract Previous coupled climate model simulations reveal that a dipole-like SST pattern with cooler (warmer) temperature over the north (south) tropical Atlantic emerges in response to a slowdown of the Atlantic meridional overturning circulation (AMOC). Using a 2½-layer reduced-gravity ocean model, a systematic investigation into oceanic processes controlling the tropical Atlantic sea surface temperature (SST) response to AMOC changes by varying the strength of northward mass transport at the open boundaries was conducted. It is found that the North Brazil Current (NBC) reverses its direction in response to a shutdown of the AMOC. Such a circulation change causes a decrease in upper equatorial ocean stratification and warming in the Gulf of Guinea and off the coast of Africa. These findings point to the importance of oceanic dynamics in the equatorial SST response to AMOC changes. Sensitivity experiments further show that the SST response relates nonlinearly to AMOC changes. The strength of the SST response increases dramatically when the AMOC strength falls below a threshold value. This nonlinear threshold behavior depends on the position of a subsurface temperature gradient forming along the boundary between the northern subtropical gyre and the tropical gyre that interacts with the western boundary current. The analysis suggests that, in order for the oceanic dynamics to have a dominant influence on tropical Atlantic SST in response to AMOC changes, two conditions must be satisfied: 1) the AMOC must weaken substantially so that the NBC flows equatorward, permitting water mass exchange between the northern subtropical and tropical gyres, and 2) the subsurface temperature front must be located in an optimal location where subsurface temperature anomalies induced by AMOC change are able to enter the equatorial zone.

scholarly journals A comparison of ocean model data and satellite observations of features affecting the growth of the North Equatorial Counter Current during the strong 1997–1998 El Niño

Ocean Science ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 565-574
Author(s):  
David J. Webb ◽  
Andrew C. Coward ◽  
Helen M. Snaith
Keyword(s):  
Sea Level ◽  
El Niño ◽  
El Nino ◽  
Ocean Model ◽  
Satellite Observations ◽  
Sea Surface ◽  
Warm Water ◽  
The North ◽  
North Equatorial Counter Current ◽  
Counter Current

Abstract. Descriptions of the ocean's role in the El Niño usually focus on equatorial Kelvin waves and the ability of such waves to change the mean thermocline depth and the sea surface temperature (SST) in the central and eastern Pacific. In contrast, starting from a study of the transport of water with temperatures greater than 28 ∘C, sufficient to trigger deep atmospheric convection, Webb (2018) found that, during the strong El Niños of 1983–1984 and 1997–1998, advection by the North Equatorial Counter Current (NECC) had a much greater impact on sea surface temperatures than processes occurring near the Equator. Webb's analysis, which supports the scheme proposed by Wyrtki (1973, 1974), made use of archived data from a high-resolution ocean model. Previously the model had been checked in a preliminary comparison against SST observations in the equatorial Pacific, but, given the contentious nature of the new analysis, the model's behaviour in key areas needs to be checked further against observations. In this paper this is done for the 1987–1988 El Niño, making use of satellite observations of SST and sea level. SST is used to check the movement of warm water near the Equator and at the latitudes of the NECC. Sea level is used to check the model results at the Equator and at 6∘ N in the North Equatorial Trough. Sea level differences between these latitudes affect the transport of the NECC, the increased transport at the start of each strong El Niño being associated with a drop in sea level at 6∘ N in the western Pacific. Later rises in sea level at the Equator increase the transport of the NECC in mid-ocean. The variability of sea level at 6∘ N is also used to compare the strength of tropical instability waves in the model and in the observations. The model showed that in a normal year these act to dilute the temperature in the core of the NECC. However their strength declined during the development of the strong El Niños, allowing the NECC to carry warm water much further than normal across the Pacific. The results of this paper should not be taken as providing proof of the hypotheses of Wyrtki (1973, 1974) or Webb (2018) but instead as a failure of a targeted study, using satellite observations, to disprove the hypotheses.

scholarly journals Changes in chlorophyll concentration and phenology in the North Sea in relation to de‐eutrophication and sea surface warming

2019 ◽  
Vol 65 (4) ◽  
pp. 828-847 ◽  
Author(s):  
Xavier Desmit ◽  
Anja Nohe ◽  
Alberto Vieira Borges ◽  
Theo Prins ◽  
Karien De Cauwer ◽  
...  
Keyword(s):  
North Sea ◽  
Chlorophyll Concentration ◽  
Sea Surface ◽  
Surface Warming ◽  
The North ◽  
The North Sea

scholarly journals High-Resolution Ocean Model Captures Large-Scale Heat Transport

Eos ◽  
2016 ◽  
Author(s):  
Sarah Stanley
Keyword(s):  
High Resolution ◽  
Heat Transport ◽  
North Atlantic ◽  
Large Scale ◽  
Ocean Model ◽  
Sea Surface ◽  
The North ◽  
Resolution Model ◽  
High Resolution Model ◽  
The North Atlantic

A lower-resolution model is sufficient to capture air-sea interactions, but a high-resolution model better simulates average sea surface temperatures in the North Atlantic.

scholarly journals Changes in extreme regional sea surface height due to an abrupt weakening of the Atlantic MOC

2014 ◽  
Vol 11 (2) ◽  
pp. 1213-1241
Author(s):  
S.-E. Brunnabend ◽  
H. A. Dijkstra ◽  
M. A. Kliphuis ◽  
B. van Werkhoven ◽  
E. Bal ◽  
...  
Keyword(s):  
North Atlantic ◽  
Gulf Stream ◽  
Sea Surface Height ◽  
Ocean Model ◽  
Meridional Overturning Circulation ◽  
Sea Surface ◽  
Sea Level Changes ◽  
The North ◽  
Meridional Overturning ◽  
Extreme Scenario

Abstract. As an extreme scenario of dynamical sea level changes, regional sea surface height (SSH) changes that occur in the North Atlantic due to an abrupt weakening of the Atlantic Meridional Overturning Circulation (AMOC) are simulated. Two versions of the same ocean-only model are used to study the effect of ocean model resolution on these SSH changes: a high-resolution (HR) strongly eddying version and a low-resolution (LR) version in which the effect of eddies are parameterized. The weakening of the AMOC is induced in both model versions by applying strong freshwater perturbations around Greenland. A rapid decrease of the AMOC in the HR version induces much shorter return times of several specific regional and coastal extremes in North Atlantic SSH than in the LR version. This effect is caused by a change in main eddy pathways associated with a change in separation latitude of the Gulf Stream.

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