scholarly journals A latitudinally banded phytoplankton response to 21st century climate change in the Southern Ocean across the CMIP5 model suite

2015 ◽  
Vol 12 (19) ◽  
pp. 5715-5734 ◽  
Author(s):  
S. Leung ◽  
A. Cabré ◽  
I. Marinov
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
21St Century ◽  
Light Availability ◽  
Southern Annular Mode ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Phytoplankton Abundance ◽  
Phytoplankton Productivity ◽  
Carbon Cycles

Abstract. Changes in Southern Ocean (SO) phytoplankton distributions with future warming have the potential to significantly alter nutrient and carbon cycles as well as higher trophic level productivity both locally and throughout the global ocean. Here we investigate the response of SO phytoplankton productivity and biomass to 21st century climate change across the CMIP5 Earth System Model suite. The models predict a zonally banded pattern of phytoplankton abundance and production changes within four regions: the subtropical (~ 30 to 40° S), transitional (~ 40 to 50° S), subpolar (~ 50 to 65° S) and Antarctic (south of ~ 65° S) bands. We find that shifts in bottom-up variables (nitrate, iron and light availability) drive changes in phytoplankton abundance and production on not only interannual, but also decadal and 100-year timescales – the timescales most relevant to climate change. Spatial patterns in the modelled mechanisms driving these biomass trends qualitatively agree with recent observations, though longer-term records are needed to separate the effects of climate change from those of interannual variability. Because much past observational work has focused on understanding the effects of the Southern Annular Mode (SAM) on biology, future work should attempt to quantify the precise influence of an increasingly positive SAM on SO biology within the CMIP5 models. Continued long-term in situ and satellite measurements of SO biology are clearly needed to confirm model findings.

scholarly journals A latitudinally-banded phytoplankton response to 21st century climate change in the Southern Ocean across the CMIP5 model suite

2015 ◽  
Vol 12 (11) ◽  
pp. 8157-8197
Author(s):  
S. Leung ◽  
A. Cabré ◽  
I. Marinov
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
21St Century ◽  
Light Availability ◽  
Southern Annular Mode ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Phytoplankton Abundance ◽  
Phytoplankton Productivity ◽  
Carbon Cycles

Abstract. Changes in Southern Ocean (SO) phytoplankton distributions with future warming have the potential to significantly alter nutrient and carbon cycles as well as higher trophic level productivity both locally and throughout the global ocean. Here we investigate the response of SO phytoplankton productivity and biomass to 21st century climate change across the CMIP5 Earth System Model suite. The models predict a zonally-banded pattern of phytoplankton abundance and production changes within 4 regions: the subtropical (~30° S to 40° S), transitional (~40° S to 50° S), subpolar (~50° S to 65° S) and Antarctic (south of ~65° S) bands. We find that shifts in bottom-up variables (nitrate, iron, and light availability) drive changes in phytoplankton abundance and production on not only interannual, but also decadal and 100-year timescales: the timescales most relevant to climate change. Spatial patterns in the modeled mechanisms driving these biomass trends qualitatively agree with recent observations, though longer-term records are needed to separate the effects of climate change from those of interannual variability. Because much past observational work has focused on understanding the effects of the Southern Annular Mode (SAM) on biology, future work should attempt to quantify the precise influence of an increasingly positive SAM on SO biology within the CMIP5 models. Continued long-term in-situ and satellite measurements of SO biology are clearly needed to confirm model findings.

Detecting Climate Fingerprints in Southern Ocean Carbon using a Biogeochemical Ocean Model

2021 ◽  
Author(s):  
Rebecca Wright ◽  
Corinne Le Quéré ◽  
Erik Buitenhuis ◽  
Dorothee Bakker
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Southern Ocean ◽  
Observational Data ◽  
Ecosystem Dynamics ◽  
Global Ocean ◽  
Subsurface Waters ◽  
Climatic Drivers ◽  
Ocean Carbon ◽  
And Storage

<p>The Southern Ocean plays an important role in the uptake, transport and storage of carbon by the global oceans. These properties are dominated by the response to the rise in anthropogenic CO<sub>2</sub> in the atmosphere, but they are modulated by climate variability and climate change. Here we explore the effect of climate variability and climate change on ocean carbon uptake and storage in the Southern Ocean. We assess the extent to which climate change may be distinguishable from the anthropogenic CO<sub>2</sub> signal and from the natural background variability. We use a combination of biogeochemical ocean modelling and observations from the GLODAPv2020 database to detect climate fingerprints in dissolved inorganic carbon (DIC).</p><p>We conduct an ensemble of hindcast model simulations of the period 1920-2019, using a global ocean biogeochemical model which incorporates plankton ecosystem dynamics based on twelve plankton functional types. We use the model ensemble to isolate the changes in DIC due to rising anthropogenic CO<sub>2</sub> alone and the changes due to climatic drivers (both climate variability and climate change), to determine their relative roles in the emerging total DIC trends and patterns. We analyse these DIC trends for a climate fingerprint over the past four decades, across spatial scales from the Southern Ocean, to basin level and down to regional ship transects. Highly sampled ship transects were extracted from GLODAPv2020 to obtain locations with the maximum spatiotemporal coverage, to reduce the inherent biases in patchy observational data. Model results were sampled to the ship transects to compare the climate fingerprints directly to the observational data.</p><p>Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 µmol/L. In the surface ocean, both anthropogenic CO<sub>2</sub> and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO<sub>2</sub> dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO<sub>2</sub> generally acts to increase DIC except in the subsurface waters at lower latitudes, while climatic drivers act to decrease DIC concentration. The combined fingerprint of anthropogenic CO<sub>2</sub> and climatic drivers on DIC concentration is for an increasing trend at the surface and decreasing trends in low latitude subsurface waters. Preliminary comparison of the model fingerprints to observational ship transects will also be presented.</p>

scholarly journals The effects of climate change on persistent organic pollutants (POPs) in the North Sea

2013 ◽  
Vol 10 (5) ◽  
pp. 1525-1557
Author(s):  
K. O'Driscoll ◽  
B. Mayer ◽  
J. Su ◽  
M. Mathis
Keyword(s):  
Climate Change ◽  
Organic Pollutants ◽  
North Sea ◽  
21St Century ◽  
Persistent Organic Pollutants ◽  
Global Ocean ◽  
Open Boundary ◽  
The North ◽  
The Future ◽  
The North Sea

Abstract. The fate and cycling of two selected legacy persistent organic pollutants (POPs), PCB 153 and γ-HCH, in the North Sea in the 21st century have been modelled with combined hydrodynamic and fate and transport ocean models. To investigate the impact of climate variability on POPs in the North Sea in the 21st century, future scenario model runs for three 10 yr periods to the year 2100 using plausible levels of both in situ concentrations and atmospheric, river and open boundary inputs are performed. Since estimates of future concentration levels of POPs in the atmosphere, oceans and rivers are not available, our approach was to reutilise 2005 values in the atmosphere, rivers and at the open ocean boundaries for every year of the simulations. In this way, we attribute differences between the three 10 yr simulations to climate change only. For the HAMSOM and atmospheric forcing, results of the IPCC A1B (SRES) 21st century scenario are utilised, where surface forcing is provided by the REMO downscaling of the ECHAM5 global atmospheric model, and open boundary conditions are provided by the MPIOM global ocean model. Dry gas deposition and volatilisation of γ-HCH increase in the future relative to the present. In the water column, total mass of γ-HCH and PCB 153 remain fairly steady in all three runs. In sediment, γ-HCH increases in the future runs, relative to the present, while PCB 153 in sediment decreases exponentially in all three runs, but even faster in the future, both of which are the result of climate change. Annual net sinks exceed sources at the ends of all periods.

scholarly journals Dominance of the Southern Ocean in Anthropogenic Carbon and Heat Uptake in CMIP5 Models

2015 ◽  
Vol 28 (2) ◽  
pp. 862-886 ◽  
Author(s):  
Thomas L. Frölicher ◽  
Jorge L. Sarmiento ◽  
David J. Paynter ◽  
John P. Dunne ◽  
John P. Krasting ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Carbon Storage ◽  
Heat Storage ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Co2 Uptake ◽  
Anthropogenic Co2 ◽  
Recent Climate ◽  
Heat Uptake ◽  
Anthropogenic Carbon

Abstract The authors assess the uptake, transport, and storage of oceanic anthropogenic carbon and heat over the period 1861–2005 in a new set of coupled carbon–climate Earth system models conducted for the fifth phase of the Coupled Model Intercomparison Project (CMIP5), with a particular focus on the Southern Ocean. Simulations show that the Southern Ocean south of 30°S, occupying 30% of global surface ocean area, accounts for 43% ± 3% (42 ± 5 Pg C) of anthropogenic CO2 and 75% ± 22% (23 ± 9 × 1022 J) of heat uptake by the ocean over the historical period. Northward transport out of the Southern Ocean is vigorous, reducing the storage to 33 ± 6 Pg anthropogenic carbon and 12 ± 7 × 1022 J heat in the region. The CMIP5 models, as a class, tend to underestimate the observation-based global anthropogenic carbon storage but simulate trends in global ocean heat storage over the last 50 years within uncertainties of observation-based estimates. CMIP5 models suggest global and Southern Ocean CO2 uptake have been largely unaffected by recent climate variability and change. Anthropogenic carbon and heat storage show a common broad-scale pattern of change, but ocean heat storage is more structured than ocean carbon storage. The results highlight the significance of the Southern Ocean for the global climate and as the region where models differ the most in representation of anthropogenic CO2 and, in particular, heat uptake.

scholarly journals Environmental forcing and Southern Ocean marine predator populations: effects of climate change and variability

2007 ◽  
Vol 362 (1488) ◽  
pp. 2351-2365 ◽  
Author(s):  
P.N Trathan ◽  
J Forcada ◽  
E.J Murphy
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Food Webs ◽  
Time Scales ◽  
Trophic Level ◽  
Global Ocean ◽  
Ecosystem Structure ◽  
Marine Predator ◽  
Enso Events ◽  
Biological Responses

The Southern Ocean is a major component within the global ocean and climate system and potentially the location where the most rapid climate change is most likely to happen, particularly in the high-latitude polar regions. In these regions, even small temperature changes can potentially lead to major environmental perturbations. Climate change is likely to be regional and may be expressed in various ways, including alterations to climate and weather patterns across a variety of time-scales that include changes to the long interdecadal background signals such as the development of the El Niño–Southern Oscillation (ENSO). Oscillating climate signals such as ENSO potentially provide a unique opportunity to explore how biological communities respond to change. This approach is based on the premise that biological responses to shorter-term sub-decadal climate variability signals are potentially the best predictor of biological responses over longer time-scales. Around the Southern Ocean, marine predator populations show periodicity in breeding performance and productivity, with relationships with the environment driven by physical forcing from the ENSO region in the Pacific. Wherever examined, these relationships are congruent with mid-trophic-level processes that are also correlated with environmental variability. The short-term changes to ecosystem structure and function observed during ENSO events herald potential long-term changes that may ensue following regional climate change. For example, in the South Atlantic, failure of Antarctic krill recruitment will inevitably foreshadow recruitment failures in a range of higher trophic-level marine predators. Where predator species are not able to accommodate by switching to other prey species, population-level changes will follow. The Southern Ocean, though oceanographically interconnected, is not a single ecosystem and different areas are dominated by different food webs. Where species occupy different positions in different regional food webs, there is the potential to make predictions about future change scenarios.

scholarly journals Multiple stressors of ocean ecosystems in the 21st century: projections with CMIP5 models

2013 ◽  
Vol 10 (2) ◽  
pp. 3627-3676 ◽  
Author(s):  
L. Bopp ◽  
L. Resplandy ◽  
J. C. Orr ◽  
S. C. Doney ◽  
J. P. Dunne ◽  
...  
Keyword(s):  
21St Century ◽  
Primary Productivity ◽  
Multiple Stressors ◽  
Sea Surface ◽  
Marine Phytoplankton ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Regional Patterns ◽  
Ocean Ecosystems ◽  
The Tropics

Abstract. Ocean ecosystems are increasingly stressed by human-induced changes of their physical, chemical and biological environment. Among these changes, warming, acidification, deoxygenation and changes in primary productivity by marine phytoplankton can be considered as four of the major stressors of open ocean ecosystems. Due to rising atmospheric CO2 in the coming decades, these changes will be amplified. Here, we use the most recent simulations performed in the framework of the Coupled Model Intercomparison Project 5 to assess how these stressors may evolve over the course of the 21st century. The 10 Earth System Models used here project similar trends in ocean warming, acidification, deoxygenation and reduced primary productivity for each of the IPCC's representative concentration parthways (RCP) over the 21st century. For the "business-as-usual" scenario RCP8.5, the model-mean changes in 2090s (compared to 1990s) for sea surface temperature, sea surface pH, global O2 content and integrated primary productivity amount to +2.73 °C, −0.33 pH unit, −3.45% and −8.6%, respectively. For the high mitigation scenario RCP2.6, corresponding changes are +0.71 °C, −0.07 pH unit, −1.81% and −2.0% respectively, illustrating the effectiveness of extreme mitigation strategies. Although these stressors operate globally, they display distinct regional patterns. Large decreases in O2 and in pH are simulated in global ocean intermediate and mode waters, whereas large reductions in primary production are simulated in the tropics and in the North Atlantic. Although temperature and pH projections are robust across models, the same does not hold for projections of sub-surface O2 concentrations in the tropics and global and regional changes in net primary productivity.

Changes in the Antarctic sea ice ecosystem: potential effects on krill and baleen whales

2008 ◽  
Vol 59 (5) ◽  
pp. 361 ◽  
Author(s):  
Stephen Nicol ◽  
Anthony Worby ◽  
Rebecca Leaper
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Sea Ice ◽  
Ocean Circulation ◽  
Trophic Levels ◽  
Global Ocean ◽  
Ecological Change ◽  
Cetacean Species ◽  
Baleen Whales ◽  
The Antarctic

The annual formation and loss of some 15 million km2 of sea ice around the Antarctic significantly affects global ocean circulation, particularly through the formation of dense bottom water. As one of the most profound seasonal changes on Earth, the formation and decay of sea ice plays a major role in climate processes. It is also likely to be impacted by climate change, potentially changing the productivity of the Antarctic region. The sea ice zone supports much wildlife, particularly large vertebrates such as seals, seabirds and whales, some exploited to near extinction. Cetacean species in the Southern Ocean will be directly impacted by changes in sea ice patterns as well as indirectly by changes in their principal prey, Antarctic krill, affected by modifications to their own environment through climate change. Understanding how climate change will affect species at all trophic levels in the Southern Ocean requires new approaches and integrated research programs. This review focuses on the current state of knowledge of the sea ice zone and examines the potential for climatic and ecological change in the region. In the context of changes already documented for seals and seabirds, it discusses potential effects on the most conspicuous vertebrate of the region, baleen whales.

scholarly journals Multiple stressors of ocean ecosystems in the 21st century: projections with CMIP5 models

2013 ◽  
Vol 10 (10) ◽  
pp. 6225-6245 ◽  
Author(s):  
L. Bopp ◽  
L. Resplandy ◽  
J. C. Orr ◽  
S. C. Doney ◽  
J. P. Dunne ◽  
...  
Keyword(s):  
21St Century ◽  
Primary Productivity ◽  
Multiple Stressors ◽  
Sea Surface ◽  
Marine Phytoplankton ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Regional Patterns ◽  
Ocean Ecosystems ◽  
The Tropics

Abstract. Ocean ecosystems are increasingly stressed by human-induced changes of their physical, chemical and biological environment. Among these changes, warming, acidification, deoxygenation and changes in primary productivity by marine phytoplankton can be considered as four of the major stressors of open ocean ecosystems. Due to rising atmospheric CO2 in the coming decades, these changes will be amplified. Here, we use the most recent simulations performed in the framework of the Coupled Model Intercomparison Project 5 to assess how these stressors may evolve over the course of the 21st century. The 10 Earth system models used here project similar trends in ocean warming, acidification, deoxygenation and reduced primary productivity for each of the IPCC's representative concentration pathways (RCPs) over the 21st century. For the "business-as-usual" scenario RCP8.5, the model-mean changes in the 2090s (compared to the 1990s) for sea surface temperature, sea surface pH, global O2 content and integrated primary productivity amount to +2.73 (±0.72) °C, −0.33 (±0.003) pH unit, −3.45 (±0.44)% and −8.6 (±7.9)%, respectively. For the high mitigation scenario RCP2.6, corresponding changes are +0.71 (±0.45) °C, −0.07 (±0.001) pH unit, −1.81 (±0.31)% and −2.0 (±4.1)%, respectively, illustrating the effectiveness of extreme mitigation strategies. Although these stressors operate globally, they display distinct regional patterns and thus do not change coincidentally. Large decreases in O2 and in pH are simulated in global ocean intermediate and mode waters, whereas large reductions in primary production are simulated in the tropics and in the North Atlantic. Although temperature and pH projections are robust across models, the same does not hold for projections of subsurface O2 concentrations in the tropics and global and regional changes in net primary productivity. These high uncertainties in projections of primary productivity and subsurface oxygen prompt us to continue inter-model comparisons to understand these model differences, while calling for caution when using the CMIP5 models to force regional impact models.

scholarly journals Influence of the Southern Annular Mode on Projected Weakening of the Atlantic Meridional Overturning Circulation

2013 ◽  
Vol 26 (20) ◽  
pp. 8017-8036 ◽  
Author(s):  
Peter T. Spooner ◽  
Helen L. Johnson ◽  
Tim J. Woollings
Keyword(s):  
Climate Change ◽  
Southern Ocean ◽  
Greenhouse Gas ◽  
Climate Models ◽  
Atlantic Meridional Overturning Circulation ◽  
Southern Annular Mode ◽  
Meridional Overturning Circulation ◽  
Overturning Circulation ◽  
Annular Mode ◽  
Meridional Overturning

Abstract Coupled climate models predict density-driven weakening of the Atlantic meridional overturning circulation (AMOC) under greenhouse gas forcing, with considerable spread in the response between models. There is also a large spread in the predicted increase of the southern annular mode (SAM) index across these models. Regression analysis across model space using 11 non-eddy-resolving models suggests that up to 35% of the intermodel spread in the AMOC response may be associated with uncertainty in the magnitude of the increase in the SAM. Models with a large, positive SAM index response generally display a smaller weakening of the AMOC under greenhouse gas forcing. The initial AMOC strength is also a major cause of intermodel spread in its response to climate change. The increase in the SAM acts to reduce the weakening of the AMOC over the next century by around ⅓, through increases in wind stress over the Southern Ocean, northward Ekman transport, and upwelling around Antarctica. The SAM response is also related to an increase in the northward salt flux across 30°S and to salinity anomalies in the high-latitude North Atlantic. These provide a positive feedback by further reinforcement of the AMOC. The results suggest that, compared with the real ocean where eddies oppose wind-driven changes in Southern Ocean circulation, climate models underestimate the effects of anthropogenic climate change on the AMOC.

scholarly journals Changes in Global Ocean Bottom Properties and Volume Transports in CMIP5 Models under Climate Change Scenarios*

2015 ◽  
Vol 28 (8) ◽  
pp. 2917-2944 ◽  
Author(s):  
Céline Heuzé ◽  
Karen J. Heywood ◽  
David P. Stevens ◽  
Jeff K. Ridley
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
Bottom Water ◽  
Global Ocean ◽  
Cmip5 Models ◽  
Climate Change Scenarios ◽  
Antarctic Bottom Water ◽  
The North ◽  
The Mean ◽  
The North Atlantic

Abstract Changes in bottom temperature, salinity, and density in the global ocean by 2100 for CMIP5 climate models are investigated for the climate change scenarios RCP4.5 and RCP8.5. The mean of 24 models shows a decrease in density in all deep basins, except the North Atlantic, which becomes denser. The individual model responses to climate change forcing are more complex: regarding temperature, the 24 models predict a warming of the bottom layer of the global ocean; in salinity, there is less agreement regarding the sign of the change, especially in the Southern Ocean. The magnitude and equatorward extent of these changes also vary strongly among models. The changes in properties can be linked with changes in the mean transport of key water masses. The Atlantic meridional overturning circulation weakens in most models and is directly linked to changes in bottom density in the North Atlantic. These changes are the result of the intrusion of modified Antarctic Bottom Water, made possible by the decrease in North Atlantic Deep Water formation. In the Indian, Pacific, and South Atlantic Oceans, changes in bottom density are congruent with the weakening in Antarctic Bottom Water transport through these basins. The authors argue that the greater the 1986–2005 meridional transports, the more changes have propagated equatorward by 2100. However, strong decreases in density over 100 yr of climate change cause a weakening of the transports. The speed at which these property changes reach the deep basins is critical for a correct assessment of the heat storage capacity of the oceans as well as for predictions of future sea level rise.

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