The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland
Identifying the drivers of Arctic climate variability is essential for understanding the recent rapid changes in local climate and determining the mechanisms that cause them. Remote tropical sea surface temperatures (SST) have been identified in previous studies as having contributed to the recent p...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/276908 2023-07-30T04:01:01+02:00 The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland McCrystall, Michelle Roisin 2018-06-11T13:12:48Z application/pdf https://doi.org/10.17863/CAM.24190 https://www.repository.cam.ac.uk/handle/1810/276908 en eng St Edmunds College Department of Chemistry University of Cambridge doi:10.17863/CAM.24190 https://www.repository.cam.ac.uk/handle/1810/276908 All rights reserved https://www.rioxx.net/licenses/all-rights-reserved/ Arctic climate Arctic amplifcation Teleconnections Tropic to Arctic teleconnections Arctic circulation Arctic warming Rossby Waves Rossby Wave sources Tropical SST perturbations Thesis Doctoral Doctor of Philosophy (PhD) PhD 2018 ftunivcam https://doi.org/10.17863/CAM.24190 2023-07-10T21:52:35Z Identifying the drivers of Arctic climate variability is essential for understanding the recent rapid changes in local climate and determining the mechanisms that cause them. Remote tropical sea surface temperatures (SST) have been identified in previous studies as having contributed to the recent positive trends in surface temperature and geopotential height at 200 hPa over north Canada and Greenland (1979-2012) through poleward propagating Rossby waves. However, the source and direction of wave propagation on to north Canada and Greenland (NCG) differs across climate datasets indicating that there are still uncertainties surrounding the mechanisms for how the tropics influence the NCG climate. This thesis aims to further investigate the robustness of the trends over NCG and understand how circulation in this region responds to imposed tropical SST perturbations. The eddy 200 hPa geopotential height (Z200) trends over NCG are assessed in a number of different datasets and compared to the response of eddy Z200 over NCG to imposed tropical SST perturbations in a number of sensitivity studies using the HadGEM3 atmosphere-only model. These model experiments are forced with observed differences in SSTs from the beginning and end of the satellite record (1979-1988 and 2003-2012), with spatial perturbations for [i] the entire tropics, [ii] global SSTs, [iii] the tropical Pacific only, [iv] the tropical Atlantic SST only, [v] the tropical Indian Ocean only. The positive spatial trends of eddy Z200 over NCG from ERA-Interim reanalysis is largely captured in ensemble means of two available climate datasets, UPSCALE and AMIP, indicating that this is a robust climate pattern, however, these trends appear to be stronger in the latter part of the record specifically over the UPSCALE period (1985 to 2011). The model sensitivity studies show that a negative eddy Z200 anomaly over NCG was found in response to all imposed tropical SST perturbations (2003-2012) relative to a background state (1979-1988). This was due a stationary ... Doctoral or Postdoctoral Thesis Arctic Greenland Apollo - University of Cambridge Repository Arctic Canada Greenland Indian Pacific |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
Arctic climate Arctic amplifcation Teleconnections Tropic to Arctic teleconnections Arctic circulation Arctic warming Rossby Waves Rossby Wave sources Tropical SST perturbations |
spellingShingle |
Arctic climate Arctic amplifcation Teleconnections Tropic to Arctic teleconnections Arctic circulation Arctic warming Rossby Waves Rossby Wave sources Tropical SST perturbations McCrystall, Michelle Roisin The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
topic_facet |
Arctic climate Arctic amplifcation Teleconnections Tropic to Arctic teleconnections Arctic circulation Arctic warming Rossby Waves Rossby Wave sources Tropical SST perturbations |
description |
Identifying the drivers of Arctic climate variability is essential for understanding the recent rapid changes in local climate and determining the mechanisms that cause them. Remote tropical sea surface temperatures (SST) have been identified in previous studies as having contributed to the recent positive trends in surface temperature and geopotential height at 200 hPa over north Canada and Greenland (1979-2012) through poleward propagating Rossby waves. However, the source and direction of wave propagation on to north Canada and Greenland (NCG) differs across climate datasets indicating that there are still uncertainties surrounding the mechanisms for how the tropics influence the NCG climate. This thesis aims to further investigate the robustness of the trends over NCG and understand how circulation in this region responds to imposed tropical SST perturbations. The eddy 200 hPa geopotential height (Z200) trends over NCG are assessed in a number of different datasets and compared to the response of eddy Z200 over NCG to imposed tropical SST perturbations in a number of sensitivity studies using the HadGEM3 atmosphere-only model. These model experiments are forced with observed differences in SSTs from the beginning and end of the satellite record (1979-1988 and 2003-2012), with spatial perturbations for [i] the entire tropics, [ii] global SSTs, [iii] the tropical Pacific only, [iv] the tropical Atlantic SST only, [v] the tropical Indian Ocean only. The positive spatial trends of eddy Z200 over NCG from ERA-Interim reanalysis is largely captured in ensemble means of two available climate datasets, UPSCALE and AMIP, indicating that this is a robust climate pattern, however, these trends appear to be stronger in the latter part of the record specifically over the UPSCALE period (1985 to 2011). The model sensitivity studies show that a negative eddy Z200 anomaly over NCG was found in response to all imposed tropical SST perturbations (2003-2012) relative to a background state (1979-1988). This was due a stationary ... |
format |
Doctoral or Postdoctoral Thesis |
author |
McCrystall, Michelle Roisin |
author_facet |
McCrystall, Michelle Roisin |
author_sort |
McCrystall, Michelle Roisin |
title |
The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
title_short |
The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
title_full |
The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
title_fullStr |
The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
title_full_unstemmed |
The impact of tropical sea surface temperature perturbations on atmospheric circulation over north Canada and Greenland |
title_sort |
impact of tropical sea surface temperature perturbations on atmospheric circulation over north canada and greenland |
publisher |
St Edmunds College |
publishDate |
2018 |
url |
https://doi.org/10.17863/CAM.24190 https://www.repository.cam.ac.uk/handle/1810/276908 |
geographic |
Arctic Canada Greenland Indian Pacific |
geographic_facet |
Arctic Canada Greenland Indian Pacific |
genre |
Arctic Greenland |
genre_facet |
Arctic Greenland |
op_relation |
doi:10.17863/CAM.24190 https://www.repository.cam.ac.uk/handle/1810/276908 |
op_rights |
All rights reserved https://www.rioxx.net/licenses/all-rights-reserved/ |
op_doi |
https://doi.org/10.17863/CAM.24190 |
_version_ |
1772811725388644352 |