Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts
The Antarctic climate has undergone complex changes over the last fifty years, driven largely by stratospheric ozone depletion. By the end of this century, under the current trajectory of anthropogenic emissions, the climate of Antarctica is projected to be significantly wetter, warmer and prone to...
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Format: | Thesis |
Language: | English |
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2019
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Online Access: | https://doi.org/10.7916/d8-w437-kn51 |
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ftcolumbiauniv:oai:academiccommons.columbia.edu:10.7916/d8-w437-kn51 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Columbia University: Academic Commons |
op_collection_id |
ftcolumbiauniv |
language |
English |
topic |
Climatic changes Climatic changes--Mathematical models Atmosphere Ozone layer depletion Sea ice--Environmental aspects |
spellingShingle |
Climatic changes Climatic changes--Mathematical models Atmosphere Ozone layer depletion Sea ice--Environmental aspects England, Mark Ross Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
topic_facet |
Climatic changes Climatic changes--Mathematical models Atmosphere Ozone layer depletion Sea ice--Environmental aspects |
description |
The Antarctic climate has undergone complex changes over the last fifty years, driven largely by stratospheric ozone depletion. By the end of this century, under the current trajectory of anthropogenic emissions, the climate of Antarctica is projected to be significantly wetter, warmer and prone to the collapse of ice shelves and loss of sea ice cover. The overarching aim of this thesis is to increase our understanding of recent and projected Antarctic climate change and its drivers. We also investigate the potential global implications of these changes and show that the effects will not be limited to the southern high latitudes. In the first half, we investigate the drivers of Antarctic climate change over the observational period. Specifically, we study the influence of the stratosphere on the southern high latitude surface climate, through stratosphere-troposphere dynamic coupling as well as stratospheric ozone depletion. We examine the impact of these on the Amundsen Sea Low, a key circulation feature near West Antarctica. We demonstrate using reanalysis that stratospheric heat flux extremes are linked to high latitude tropospheric anomalies in the Amundsen Sea region. During extreme negative (positive) events there is a westward (eastward) shift of the Amundsen Sea Low, a warming (cooling) and increase (decrease) of geopotential height over the Amundsen and Bellingshausen Seas. We find that most CMIP5 models are not able to capture this relationship. Next, we demonstrate that, since 1965, stratospheric ozone depletion has acted to deepen the Amundsen Sea Low in austral summer by 1 hPa per decade. This result was consistent across two different comprehensive climate models, each with very different model physics and climate sensitivity. It must be noted that the ozone depletion signal on the Amundsen Sea Low is small compared to the internal climate variability in this region. Using ensembles of model integrations and analysing them over the full period of ozone depletion (which started a couple of decades before the satellite era) is necessary to detect a robust signal. In the second half, we investigate the effects of future Antarctic climate change, specifically the effects of projected sea ice loss over the coming century. Climate model simulations are used to isolate the effect of end-of-the-century Antarctic sea ice loss which is compared and contrasted with the effects of projected Arctic sea ice loss. We first study the effects of projected Antarctic sea ice loss used atmosphere-only simulations. As for the Arctic, results indicated that Antarctic sea ice loss will act to shift the tropospheric jet equatorward, an internal negative feedback to the poleward shift associated with increased greenhouse gases. Antarctic sea ice loss is shown to have an important effect throughout the year whereas Arctic sea ice loss will have more seasonally varying impacts. Building upon these results we the use the same climate model but in a fully coupled setup to study the effects of projected Antarctic sea ice loss on the climate system. We show that both Arctic and Antarctic sea ice loss will have important global effects, causing a ‘mini global warming’ signal. The tropical response to Antarctic sea ice loss is shown to be remarkably similar to that of Arctic sea ice loss, with enhanced warming in the Eastern Tropical Pacific and increased precipitation throughout much of the equatorial Pacific. These results highlight how intimately coupled the Antarctic climate is to the rest of the climate system. |
format |
Thesis |
author |
England, Mark Ross |
author_facet |
England, Mark Ross |
author_sort |
England, Mark Ross |
title |
Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
title_short |
Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
title_full |
Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
title_fullStr |
Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
title_full_unstemmed |
Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts |
title_sort |
understanding observed and projected climate changes in the antarctic, and their global impacts |
publishDate |
2019 |
url |
https://doi.org/10.7916/d8-w437-kn51 |
geographic |
Arctic Antarctic The Antarctic Austral West Antarctica Amundsen Sea Pacific |
geographic_facet |
Arctic Antarctic The Antarctic Austral West Antarctica Amundsen Sea Pacific |
genre |
Amundsen Sea Antarc* Antarctic Antarctica Arctic Climate change Global warming Ice Shelves Sea ice West Antarctica |
genre_facet |
Amundsen Sea Antarc* Antarctic Antarctica Arctic Climate change Global warming Ice Shelves Sea ice West Antarctica |
op_relation |
https://doi.org/10.7916/d8-w437-kn51 |
op_doi |
https://doi.org/10.7916/d8-w437-kn51 |
_version_ |
1766375537548197888 |
spelling |
ftcolumbiauniv:oai:academiccommons.columbia.edu:10.7916/d8-w437-kn51 2023-05-15T13:23:48+02:00 Understanding Observed and Projected Climate Changes in the Antarctic, and their Global Impacts England, Mark Ross 2019 https://doi.org/10.7916/d8-w437-kn51 English eng https://doi.org/10.7916/d8-w437-kn51 Climatic changes Climatic changes--Mathematical models Atmosphere Ozone layer depletion Sea ice--Environmental aspects Theses 2019 ftcolumbiauniv https://doi.org/10.7916/d8-w437-kn51 2019-07-20T22:19:29Z The Antarctic climate has undergone complex changes over the last fifty years, driven largely by stratospheric ozone depletion. By the end of this century, under the current trajectory of anthropogenic emissions, the climate of Antarctica is projected to be significantly wetter, warmer and prone to the collapse of ice shelves and loss of sea ice cover. The overarching aim of this thesis is to increase our understanding of recent and projected Antarctic climate change and its drivers. We also investigate the potential global implications of these changes and show that the effects will not be limited to the southern high latitudes. In the first half, we investigate the drivers of Antarctic climate change over the observational period. Specifically, we study the influence of the stratosphere on the southern high latitude surface climate, through stratosphere-troposphere dynamic coupling as well as stratospheric ozone depletion. We examine the impact of these on the Amundsen Sea Low, a key circulation feature near West Antarctica. We demonstrate using reanalysis that stratospheric heat flux extremes are linked to high latitude tropospheric anomalies in the Amundsen Sea region. During extreme negative (positive) events there is a westward (eastward) shift of the Amundsen Sea Low, a warming (cooling) and increase (decrease) of geopotential height over the Amundsen and Bellingshausen Seas. We find that most CMIP5 models are not able to capture this relationship. Next, we demonstrate that, since 1965, stratospheric ozone depletion has acted to deepen the Amundsen Sea Low in austral summer by 1 hPa per decade. This result was consistent across two different comprehensive climate models, each with very different model physics and climate sensitivity. It must be noted that the ozone depletion signal on the Amundsen Sea Low is small compared to the internal climate variability in this region. Using ensembles of model integrations and analysing them over the full period of ozone depletion (which started a couple of decades before the satellite era) is necessary to detect a robust signal. In the second half, we investigate the effects of future Antarctic climate change, specifically the effects of projected sea ice loss over the coming century. Climate model simulations are used to isolate the effect of end-of-the-century Antarctic sea ice loss which is compared and contrasted with the effects of projected Arctic sea ice loss. We first study the effects of projected Antarctic sea ice loss used atmosphere-only simulations. As for the Arctic, results indicated that Antarctic sea ice loss will act to shift the tropospheric jet equatorward, an internal negative feedback to the poleward shift associated with increased greenhouse gases. Antarctic sea ice loss is shown to have an important effect throughout the year whereas Arctic sea ice loss will have more seasonally varying impacts. Building upon these results we the use the same climate model but in a fully coupled setup to study the effects of projected Antarctic sea ice loss on the climate system. We show that both Arctic and Antarctic sea ice loss will have important global effects, causing a ‘mini global warming’ signal. The tropical response to Antarctic sea ice loss is shown to be remarkably similar to that of Arctic sea ice loss, with enhanced warming in the Eastern Tropical Pacific and increased precipitation throughout much of the equatorial Pacific. These results highlight how intimately coupled the Antarctic climate is to the rest of the climate system. Thesis Amundsen Sea Antarc* Antarctic Antarctica Arctic Climate change Global warming Ice Shelves Sea ice West Antarctica Columbia University: Academic Commons Arctic Antarctic The Antarctic Austral West Antarctica Amundsen Sea Pacific |