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

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.

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On the impact of sea ice in a global ocean circulation model

Annals of Glaciology ◽

10.3189/s0260305500013884 ◽

1997 ◽

Vol 25 ◽

pp. 111-115 ◽

Cited By ~ 3

Author(s):

Achim Stössel

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ocean Circulation ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

Deep Ocean ◽

Global Ocean ◽

Convective Activity ◽

The Impact

This paper investigates the long-term impact of sea ice on global climate using a global sea-ice–ocean general circulation model (OGCM). The sea-ice component involves state-of-the-art dynamics; the ocean component consists of a 3.5° × 3.5° × 11 layer primitive-equation model. Depending on the physical description of sea ice, significant changes are detected in the convective activity, in the hydrographic properties and in the thermohaline circulation of the ocean model. Most of these changes originate in the Southern Ocean, emphasizing the crucial role of sea ice in this marginally stably stratified region of the world's oceans. Specifically, if the effect of brine release is neglected, the deep layers of the Southern Ocean warm up considerably; this is associated with a weakening of the Southern Hemisphere overturning cell. The removal of the commonly used “salinity enhancement” leads to a similar effect. The deep-ocean salinity is almost unaffected in both experiments. Introducing explicit new-ice thickness growth in partially ice-covered gridcells leads to a substantial increase in convective activity, especially in the Southern Ocean, with a concomitant significant cooling and salinification of the deep ocean. Possible mechanisms for the resulting interactions between sea-ice processes and deep-ocean characteristics are suggested.

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Last Glacial Maximum Antarctic sea ice linked with global mean ocean temperature: evidence from PMIP3, PMIP4 and MIROC-4m simulations

10.5194/egusphere-egu21-3550 ◽

2021 ◽

Author(s):

Tristan Vadsaria ◽

Sam Sherriff-Tadano ◽

Ayako Abe-Ouchi ◽

Takashi Obase ◽

Wing-Le Chan ◽

...

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Last Glacial Maximum ◽

Ocean Circulation ◽

Glacial Maximum ◽

Ocean Temperature ◽

Sea Ice Extent ◽

Last Glacial ◽

Antarctic Sea Ice ◽

The Antarctic

Southern Ocean sea ice and oceanic fronts are known to play an important role on the climate system, carbon cycles, bottom ocean circulation, and Antarctic ice sheet. However, many models of the previous Past-climate Model Intercomparison Project (PMIP) underestimated sea-ice extent (SIE) for the Last Glacial Maximum (LGM)(Roche et al., 2012; Marzocchi and Jensen, 2017), mainly because of surface bias (Flato et al., 2013) that may have an impact on mean ocean temperature (MOT). Indeed, recent studies further suggest an important link between Southern Ocean sea ice and mean ocean temperature (Ferrari et al., 2014; Bereiter et al., 2018 among others). Misrepresent the Antarctic sea-ice extent could highly impact deep ocean circulation, the heat transport and thus the MOT. In this study, we will stress the relationship between the distribution of Antarctic sea-ice extent and the MOT through the analysis of the PMIP3 and PMIP4 exercise and by using a set of MIROC models. To date, the latest version of MIROC improve its representation of the LGM Antarctic sea-ice extent, affecting the deep circulation and the MOT distribution (Sherriff-Tadano et al., under review).Our results show that available PMIP4 models have an overall improvement in term of LGM sea-ice extent compared to PMIP3, associated to colder deep and bottom ocean temperature. Focusing on MIROC (4m) models, we show that models accounting for Southern Ocean sea-surface temperature (SST) bias correction reproduce an Antarctic sea-ice extent, 2D-distribution, and seasonal amplitude in good agreement with proxy-based data. Finally, using PMIP-MIROC analyze, we show that it exists a relationship between the maximum SIE and the MOT, modulated by the Antarctic intermediate and bottom waters.

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Impacts of Interactive Stratospheric Chemistry on Antarctic and Southern Ocean Climate Change in the Goddard Earth Observing System, Version 5 (GEOS-5)

Journal of Climate ◽

10.1175/jcli-d-15-0572.1 ◽

2016 ◽

Vol 29 (9) ◽

pp. 3199-3218 ◽

Cited By ~ 17

Author(s):

Feng Li ◽

Yury V. Vikhliaev ◽

Paul A. Newman ◽

Steven Pawson ◽

Judith Perlwitz ◽

...

Keyword(s):

Climate Change ◽

Southern Ocean ◽

Sea Ice ◽

Ozone Depletion ◽

Stratospheric Ozone ◽

Meridional Overturning Circulation ◽

Stratospheric Chemistry ◽

Earth Observing System ◽

Antarctic Sea Ice ◽

The Antarctic

Abstract Stratospheric ozone depletion plays a major role in driving climate change in the Southern Hemisphere. To date, many climate models prescribe the stratospheric ozone layer’s evolution using monthly and zonally averaged ozone fields. However, the prescribed ozone underestimates Antarctic ozone depletion and lacks zonal asymmetries. This study investigates the impact of using interactive stratospheric chemistry instead of prescribed ozone on climate change simulations of the Antarctic and Southern Ocean. Two sets of 1960–2010 ensemble transient simulations are conducted with the coupled ocean version of the Goddard Earth Observing System Model, version 5: one with interactive stratospheric chemistry and the other with prescribed ozone derived from the same interactive simulations. The model’s climatology is evaluated using observations and reanalysis. Comparison of the 1979–2010 climate trends between these two simulations reveals that interactive chemistry has important effects on climate change not only in the Antarctic stratosphere, troposphere, and surface, but also in the Southern Ocean and Antarctic sea ice. Interactive chemistry causes stronger Antarctic lower stratosphere cooling and circumpolar westerly acceleration during November–January. It enhances stratosphere–troposphere coupling and leads to significantly larger tropospheric and surface westerly changes. The significantly stronger surface wind stress trends cause larger increases of the Southern Ocean meridional overturning circulation, leading to year-round stronger ocean warming near the surface and enhanced Antarctic sea ice decrease.

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Climate change and cetaceans: concerns and recent developments

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315408003196 ◽

2009 ◽

Vol 89 (1) ◽

pp. 203-210 ◽

Cited By ~ 41

Author(s):

Mark P. Simmonds ◽

Wendy J. Eliott

Keyword(s):

Climate Change ◽

Sea Ice ◽

Large Scale ◽

Migratory Species ◽

Cetacean Species ◽

Baleen Whales ◽

New Information ◽

The Status ◽

Recent Developments

At least a quarter of the world's cetaceans were recently confirmed as endangered and the situation may be worse as the status of many others remains unclear. Climate change is affecting the oceans and a number of studies have recently highlighted its potential impact on cetacean species - for example, there are important linkages between sea ice and krill, the primary prey for baleen whales in Antarctica. This paper provides a synthesis of new information available on this theme and considers its implications for the future conservation and management of cetacean populations and species.The more mobile (or otherwise adaptable) cetaceans may be able to respond to climate related changes, although the extent of this adaptability is largely unknown. However, there is broad agreement that certain species and populations are likely to be especially vulnerable to climate related changes, including those with a limited habitat range, or those for which sea ice provides an important habitat for the cetacean population and/or that of their prey. International conservation bodies, such as the Convention for Migratory Species and the International Whaling Commission, are striving to address these issues. The challenges presented by climate change require an innovative, large scale, long term and multinational response from scientists, conservation managers and decision makers. This response that should encompass a precautionary approach, including addressing the detrimental effects of other factors negatively impacting populations and species.

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Orbital- and millennial-scale variability of the Antarctic Circumpolar Current over the past 140,000 years

10.21203/rs.3.rs-73426/v1 ◽

2020 ◽

Author(s):

Shuzhuang Wu ◽

Lester Lembke-Jene ◽

Frank Lamy ◽

Helge Arz ◽

Norbert Nowaczyk ◽

...

Keyword(s):

Sea Ice ◽

Ocean Circulation ◽

Antarctic Circumpolar Current ◽

Cold Water ◽

Meridional Overturning Circulation ◽

Global Ocean ◽

The Past ◽

Circumpolar Current ◽

The Antarctic ◽

Millennial Scale

Abstract The Antarctic Circumpolar Current (ACC) plays a crucial role in global ocean circulation by fostering deep-water upwelling and formation of new water masses. On geological time-scales, ACC variations are poorly constrained beyond the last glacial. Here, we reconstruct changes in ACC strength in the central Drake Passage over the past 140,000 years, based on grain-size and geochemical characteristics. We found significant glacial-interglacial changes of ACC flow speed, with reduced ACC intensity during glacials and a more vigorous circulation in interglacials. Superimposed on these orbital-scale changes are high-amplitude millennial-scale fluctuations, with ACC strength maxima correlating with diatom-based Antarctic winter sea-ice minima, particularly during full glacial conditions. We hypothesize that the ACC is closely linked to Southern Hemisphere millennial-scale climate oscillations, amplified through Antarctic sea ice extent changes. These strong ACC variations regulated Pacific-Atlantic water exchange via the “cold water route” and affected the Atlantic Meridional Overturning Circulation and marine carbon storage.

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On the impact of sea ice in a global ocean circulation model

Annals of Glaciology ◽

10.1017/s0260305500013884 ◽

1997 ◽

Vol 25 ◽

pp. 111-115 ◽

Cited By ~ 2

Author(s):

Achim Stössel

Keyword(s):

Southern Ocean ◽

Sea Ice ◽

Ocean Circulation ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

Deep Ocean ◽

Global Ocean ◽

Convective Activity ◽

The Impact

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The Effect of the Kerguelen Plateau on the Ocean Circulation

Journal of Physical Oceanography ◽

10.1175/jpo-d-15-0216.1 ◽

2016 ◽

Vol 46 (11) ◽

pp. 3385-3396 ◽

Cited By ~ 2

Author(s):

Jinbo Wang ◽

Matthew R. Mazloff ◽

Sarah T. Gille

Keyword(s):

Southern Ocean ◽

Ocean Circulation ◽

Antarctic Circumpolar Current ◽

Large Scale ◽

Pressure Field ◽

Global Ocean ◽

Kerguelen Plateau ◽

Local Pressure ◽

Circumpolar Current ◽

The Antarctic

AbstractThe Kerguelen Plateau is a major topographic feature in the Southern Ocean. Located in the Indian sector and spanning nearly 2000 km in the meridional direction from the polar to the subantarctic region, it deflects the eastward-flowing Antarctic Circumpolar Current and influences the physical circulation and biogeochemistry of the Southern Ocean. The Kerguelen Plateau is known to govern the local dynamics, but its impact on the large-scale ocean circulation has not been explored. By comparing global ocean numerical simulations with and without the Kerguelen Plateau, this study identifies two major Kerguelen Plateau effects: 1) The plateau supports a local pressure field that pushes the Antarctic Circumpolar Current northward. This process reduces the warm-water transport from the Indian to the Atlantic Ocean. 2) The plateau-generated pressure field shields the Weddell Gyre from the influence of the warmer subantarctic and subtropical waters. The first effect influences the strength of the Antarctic Circumpolar Current and the Agulhas leakage, both of which are important elements in the global thermohaline circulation. The second effect results in a zonally asymmetric response of the subpolar gyres to Southern Hemisphere wind forcing.

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Global Connectivity of Southern Ocean Ecosystems

Frontiers in Ecology and Evolution ◽

10.3389/fevo.2021.624451 ◽

2021 ◽

Vol 9 ◽

Author(s):

Eugene J. Murphy ◽

Nadine M. Johnston ◽

Eileen E. Hofmann ◽

Richard A. Phillips ◽

Jennifer A. Jackson ◽

...

Keyword(s):

Southern Ocean ◽

Ocean Basin ◽

Trophic Levels ◽

Global Ocean ◽

Antarctic Polar Front ◽

Earth System ◽

Boundary Current ◽

Ocean Ecosystems ◽

Global Connectivity ◽

The Antarctic

Southern Ocean ecosystems are globally important. Processes in the Antarctic atmosphere, cryosphere, and the Southern Ocean directly influence global atmospheric and oceanic systems. Southern Ocean biogeochemistry has also been shown to have global importance. In contrast, ocean ecological processes are often seen as largely separate from the rest of the global system. In this paper, we consider the degree of ecological connectivity at different trophic levels, linking Southern Ocean ecosystems with the global ocean, and their importance not only for the regional ecosystem but also the wider Earth system. We also consider the human system connections, including the role of Southern Ocean ecosystems in supporting society, culture, and economy in many nations, influencing public and political views and hence policy. Rather than Southern Ocean ecosystems being defined by barriers at particular oceanic fronts, ecological changes are gradual due to cross-front exchanges involving oceanographic processes and organism movement. Millions of seabirds and hundreds of thousands of cetaceans move north out of polar waters in the austral autumn interacting in food webs across the Southern Hemisphere, and a few species cross the equator. A number of species migrate into the east and west ocean-basin boundary current and continental shelf regions of the major southern continents. Human travel in and out of the Southern Ocean region includes fisheries, tourism, and scientific vessels in all ocean sectors. These operations arise from many nations, particularly in the Northern Hemisphere, and are important in local communities as well as national economic, scientific, and political activities. As a result of the extensive connectivity, future changes in Southern Ocean ecosystems will have consequences throughout the Earth system, affecting ecosystem services with socio-economic impacts throughout the world. The high level of connectivity also means that changes and policy decisions in marine ecosystems outside the Southern Ocean have consequences for ecosystems south of the Antarctic Polar Front. Knowledge of Southern Ocean ecosystems and their global connectivity is critical for interpreting current change, projecting future change impacts, and identifying integrated strategies for conserving and managing both the Southern Ocean and the broader Earth system.

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The Role of Oscillating Southern Hemisphere Westerly Winds: Global Ocean Circulation

Journal of Climate ◽

10.1175/jcli-d-19-0364.1 ◽

2020 ◽

Vol 33 (6) ◽

pp. 2111-2130

Author(s):

Woo Geun Cheon ◽

Jong-Seong Kug

Keyword(s):

Ocean Circulation ◽

North Atlantic ◽

North Pacific ◽

Global Ocean ◽

The North ◽

Westerly Winds ◽

The North Atlantic ◽

Global Ocean Circulation ◽

The Antarctic ◽

The North Pacific

AbstractIn the framework of a sea ice–ocean general circulation model coupled to an energy balance atmospheric model, an intensity oscillation of Southern Hemisphere (SH) westerly winds affects the global ocean circulation via not only the buoyancy-driven teleconnection (BDT) mode but also the Ekman-driven teleconnection (EDT) mode. The BDT mode is activated by the SH air–sea ice–ocean interactions such as polynyas and oceanic convection. The ensuing variation in the Antarctic meridional overturning circulation (MOC) that is indicative of the Antarctic Bottom Water (AABW) formation exerts a significant influence on the abyssal circulation of the globe, particularly the Pacific. This controls the bipolar seesaw balance between deep and bottom waters at the equator. The EDT mode controlled by northward Ekman transport under the oscillating SH westerly winds generates a signal that propagates northward along the upper ocean and passes through the equator. The variation in the western boundary current (WBC) is much stronger in the North Atlantic than in the North Pacific, which appears to be associated with the relatively strong and persistent Mindanao Current (i.e., the southward flowing WBC of the North Pacific tropical gyre). The North Atlantic Deep Water (NADW) formation is controlled by salt advected northward by the North Atlantic WBC.

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

10.5194/egusphere-egu21-11116 ◽

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

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 CO2 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 CO2 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).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 CO2 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.Model results show a substantial change in DIC over a 35-year period, with a range of more than +/- 30 &#181;mol/L. In the surface ocean, both anthropogenic CO2 and climatic drivers act to increase DIC concentration, with the influence of anthropogenic CO2 dominating at lower latitudes and the influence of climatic drivers dominating at higher latitudes. In the deep ocean, the anthropogenic CO2 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 CO2 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.

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