1
|
Duffy GA, Montiel F, Purich A, Fraser CI. Emerging long-term trends and interdecadal cycles in Antarctic polynyas. Proc Natl Acad Sci U S A 2024; 121:e2321595121. [PMID: 38437551 PMCID: PMC10945784 DOI: 10.1073/pnas.2321595121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Accepted: 01/28/2024] [Indexed: 03/06/2024] Open
Abstract
Polynyas, areas of open water embedded within sea ice, are a key component of ocean-atmosphere interactions that act as hotspots of sea-ice production, bottom-water formation, and primary productivity. The specific drivers of polynya dynamics remain, however, elusive and coupled climate models struggle to replicate Antarctic polynya activity. Here, we leverage a 44-y time series of Antarctic sea ice to elucidate long-term trends. We identify Antarctic-wide linear increases and a hitherto undescribed cyclical pattern of polynya activity across the Ross Sea region that potentially arises from interactions between the Amundsen Sea Low and Southern Annular Mode. While their specific drivers remain unknown, identifying these emerging patterns augments our capacity to understand the processes that influence sea ice. As we enter a potentially new age of Antarctic sea ice, this advance in understanding will, in turn, lead to more accurate predictions of environmental change, and its implications for Antarctic ecosystems.
Collapse
Affiliation(s)
- Grant A. Duffy
- Department of Marine Science, University of Otago, Dunedin9054, New Zealand
| | - Fabien Montiel
- Department of Mathematics and Statistics, University of Otago, Dunedin9054, New Zealand
| | - Ariaan Purich
- School of Earth, Atmosphere and Environment, and Australian Research Council Special Research Initiative for Securing Antarctica’s Environmental Future, Monash University, Clayton, Kulin Nations, VIC3800, Australia
| | - Ceridwen I. Fraser
- Department of Marine Science, University of Otago, Dunedin9054, New Zealand
| |
Collapse
|
2
|
Cai W, Gao L, Luo Y, Li X, Zheng X, Zhang X, Cheng X, Jia F, Purich A, Santoso A, Du Y, Holland DM, Shi JR, Xiang B, Xie SP. Southern ocean warming and its climatic impacts. Sci Bull (Beijing) 2023; 68:946-960. [PMID: 37085399 DOI: 10.1016/j.scib.2023.03.049] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 03/12/2023] [Accepted: 03/13/2023] [Indexed: 04/05/2023]
Abstract
The Southern Ocean has warmed substantially, and up to early 21st century, Antarctic stratospheric ozone depletion and increasing atmospheric CO2 have conspired to intensify Southern Ocean warming. Despite a projected ozone recovery, fluxes to the Southern Ocean of radiative heat and freshwater from enhanced precipitation and melting sea ice, ice shelves, and ice sheets are expected to increase, as is a Southern Ocean westerly poleward intensification. The warming has far-reaching climatic implications for melt of Antarctic ice shelf and ice sheet, sea level rise, and remote circulations such as the intertropical convergence zone and tropical ocean-atmosphere circulations, which affect extreme weathers, agriculture, and ecosystems. The surface warm and freshwater anomalies are advected northward by the mean circulation and deposited into the ocean interior with a zonal-mean maximum at ∼45°S. The increased momentum and buoyancy fluxes enhance the Southern Ocean circulation and water mass transformation, further increasing the heat uptake. Complex processes that operate but poorly understood include interactive ice shelves and ice sheets, oceanic eddies, tropical-polar interactions, and impact of the Southern Ocean response on the climate change forcing itself; in particular, limited observations and low resolution of climate models hinder rapid progress. Thus, projection of Southern Ocean warming will likely remain uncertain, but recent community effort has laid a solid foundation for substantial progress.
Collapse
Affiliation(s)
- Wenju Cai
- Frontiers Science Center for Deep Ocean Multispheres and Earth System and Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China; Laboratory for Ocean and Climate Dynamics, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China; Center for Southern Hemisphere Oceans Research, Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere, Hobart 7004, Australia.
| | - Libao Gao
- First Institute of Oceanography and Key Laboratory of Marine Science and Numerical Modeling, Ministry of Natural Resources, Qingdao 266061, China; Laboratory for Regional Oceanography and Numerical Modeling, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China
| | - Yiyong Luo
- Frontiers Science Center for Deep Ocean Multispheres and Earth System and Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China; Laboratory for Ocean and Climate Dynamics, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China
| | - Xichen Li
- Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Xiaotong Zheng
- Frontiers Science Center for Deep Ocean Multispheres and Earth System and Key Laboratory of Physical Oceanography, Ocean University of China, Qingdao 266100, China; Laboratory for Ocean and Climate Dynamics, Pilot National Laboratory for Marine Science and Technology, Qingdao 266237, China
| | - Xuebin Zhang
- Center for Southern Hemisphere Oceans Research, Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere, Hobart 7004, Australia
| | - Xuhua Cheng
- College of Oceanography, Hohai University, Nanjing 210098, China
| | - Fan Jia
- Key Laboratory of Ocean Circulation and Waves, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
| | - Ariaan Purich
- Climate Change Research Centre, University of New South Wales, Sydney 2052, Australia; Australian Research Council Centre of Excellence for Climate Extremes, University of New South Wales, Sydney 2052, Australia
| | - Agus Santoso
- Center for Southern Hemisphere Oceans Research, Commonwealth Scientific and Industrial Research Organisation (CSIRO) Oceans and Atmosphere, Hobart 7004, Australia; Australian Research Council Centre of Excellence for Climate Extremes, University of New South Wales, Sydney 2052, Australia
| | - Yan Du
- State Key Laboratory of Tropical Oceanography, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China; Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou 511458, China
| | - David M Holland
- Courant Institute of Mathematical Sciences, New York University, New York NY 10012, USA
| | - Jia-Rui Shi
- Woods Hole Oceanographic Institution, Woods Hole MA 02543, USA
| | - Baoqiang Xiang
- NOAA/Geophysical Fluid Dynamics Laboratory, Princeton NJ 08540, USA; University Corporation for Atmospheric Research, Boulder CO 80307, USA
| | - Shang-Ping Xie
- Scripps Institution of Oceanography, University of California San Diego, La Jolla CA 92093, USA
| |
Collapse
|
3
|
Purich A, Boschat G, Liguori G. Assessing the impact of suppressing Southern Ocean SST variability in a coupled climate model. Sci Rep 2021; 11:22069. [PMID: 34764339 PMCID: PMC8585967 DOI: 10.1038/s41598-021-01306-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2021] [Accepted: 10/20/2021] [Indexed: 11/25/2022] Open
Abstract
The Southern Ocean exerts a strong influence on global climate, regulating the storage and transport of heat, freshwater and carbon throughout the world’s oceans. While the majority of previous studies focus on how wind changes influence Southern Ocean circulation patterns, here we set out to explore potential feedbacks from the ocean to the atmosphere. To isolate the role of oceanic variability on Southern Hemisphere climate, we perform coupled climate model experiments in which Southern Ocean variability is suppressed by restoring sea surface temperatures (SST) over 40°–65°S to the model’s monthly mean climatology. We find that suppressing Southern Ocean SST variability does not impact the Southern Annular Mode, suggesting air–sea feedbacks do not play an important role in the persistence of the Southern Annular Mode in our model. Suppressing Southern Ocean SST variability does lead to robust mean-state changes in SST and sea ice. Changes in mixed layer processes and convection associated with the SST restoring lead to SST warming and a sea ice decline in southern high latitudes, and SST cooling in midlatitudes. These results highlight the impact non-linear processes can have on a model’s mean state, and the need to consider these when performing simulations of the Southern Ocean.
Collapse
Affiliation(s)
- Ariaan Purich
- ARC Centre of Excellence for Climate Extremes, Sydney, Australia. .,Climate Change Research Centre, University of New South Wales, Sydney, NSW, Australia.
| | - Ghyslaine Boschat
- ARC Centre of Excellence for Climate Extremes, Sydney, Australia.,Bureau of Meteorology, Melbourne, VIC, Australia
| | - Giovanni Liguori
- ARC Centre of Excellence for Climate Extremes, Sydney, Australia.,School of Earth, Atmosphere and Environment, Monash University, Melbourne, VIC, Australia.,Department of Physics and Astronomy, University of Bologna, Bologna, Italy
| |
Collapse
|
4
|
Boschat G, Simmonds I, Purich A, Cowan T, Pezza AB. On the use of composite analyses to form physical hypotheses: An example from heat wave - SST associations. Sci Rep 2016; 6:29599. [PMID: 27412238 PMCID: PMC4944154 DOI: 10.1038/srep29599] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 06/22/2016] [Indexed: 11/09/2022] Open
Abstract
This paper highlights some caveats in using composite analyses to form physical hypotheses on the associations between environmental variables. This is illustrated using a specific example, namely the apparent links between heat waves (HWs) and sea surface temperatures (SSTs). In this case study, a composite analysis is performed to show the large-scale and regional SST conditions observed during summer HWs in Perth, southwest Australia. Composite results initially point to the importance of the subtropical South Indian Ocean, where physically coherent SST dipole anomalies appear to form a necessary condition for HWs to develop across southwest Australia. However, sensitivity tests based on pattern correlation analyses indicate that the vast majority of days when the identified SST pattern appears are overwhelmingly not associated with observed HWs, which suggests that this is definitely not a sufficient condition for HW development. Very similar findings are obtained from the analyses of 15 coupled climate model simulations. The results presented here have pertinent implications and applications for other climate case studies, and highlight the importance of applying comprehensive statistical approaches before making physical inferences on apparent climate associations.
Collapse
Affiliation(s)
- Ghyslaine Boschat
- School of Earth Sciences, The University of Melbourne, Victoria, Australia.,Australian Research Council's Centre of Excellence for Climate System Science, Australia
| | - Ian Simmonds
- School of Earth Sciences, The University of Melbourne, Victoria, Australia
| | - Ariaan Purich
- CSIRO Oceans and Atmosphere, Aspendale, Victoria, Australia
| | - Tim Cowan
- School of Geosciences, University of Edinburgh, Edinburgh, United Kingdom
| | | |
Collapse
|
5
|
Purich A, Cai W, England MH, Cowan T. Evidence for link between modelled trends in Antarctic sea ice and underestimated westerly wind changes. Nat Commun 2016; 7:10409. [PMID: 26842498 PMCID: PMC4742833 DOI: 10.1038/ncomms10409] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 12/08/2015] [Indexed: 11/27/2022] Open
Abstract
Despite global warming, total Antarctic sea ice coverage increased over 1979-2013. However, the majority of Coupled Model Intercomparison Project phase 5 models simulate a decline. Mechanisms causing this discrepancy have so far remained elusive. Here we show that weaker trends in the intensification of the Southern Hemisphere westerly wind jet simulated by the models may contribute to this disparity. During austral summer, a strengthened jet leads to increased upwelling of cooler subsurface water and strengthened equatorward transport, conducive to increased sea ice. As the majority of models underestimate summer jet trends, this cooling process is underestimated compared with observations and is insufficient to offset warming in the models. Through the sea ice-albedo feedback, models produce a high-latitude surface ocean warming and sea ice decline, contrasting the observed net cooling and sea ice increase. A realistic simulation of observed wind changes may be crucial for reproducing the recent observed sea ice increase.
Collapse
Affiliation(s)
- Ariaan Purich
- CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, Australia
- Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Wenju Cai
- CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, Australia
| | - Matthew H. England
- Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia
- ARC Centre of Excellence for Climate System Science, University of New South Wales, Sydney, New South Wales 2052, Australia
| | - Tim Cowan
- CSIRO Oceans and Atmosphere, Aspendale, Victoria 3195, Australia
- School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FE, UK
| |
Collapse
|
6
|
Affiliation(s)
- Mohamed Makha
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia, Fax: +618‐6488‐1005
| | - Ariaan Purich
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia, Fax: +618‐6488‐1005
| | - Colin L. Raston
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia, Fax: +618‐6488‐1005
| | - Alexandre N. Sobolev
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, WA 6009, Australia, Fax: +618‐6488‐1005
| |
Collapse
|