Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework
The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0–2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features a...
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ftcopernicus:oai:publications.copernicus.org:cp58025 2023-05-15T13:11:50+02:00 Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework Singh, Hansi K. A. Hakim, Gregory J. Tardif, Robert Emile-Geay, Julien Noone, David C. 2019-04-10 application/pdf https://doi.org/10.5194/cp-14-157-2018 https://cp.copernicus.org/articles/14/157/2018/ eng eng doi:10.5194/cp-14-157-2018 https://cp.copernicus.org/articles/14/157/2018/ eISSN: 1814-9332 Text 2019 ftcopernicus https://doi.org/10.5194/cp-14-157-2018 2020-07-20T16:23:25Z The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0–2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result. Text albedo Arctic Greenland Iceland Sea ice Copernicus Publications: E-Journals Arctic Greenland Climate of the Past 14 2 157 174 |
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Copernicus Publications: E-Journals |
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English |
description |
The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0–2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50- to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result. |
format |
Text |
author |
Singh, Hansi K. A. Hakim, Gregory J. Tardif, Robert Emile-Geay, Julien Noone, David C. |
spellingShingle |
Singh, Hansi K. A. Hakim, Gregory J. Tardif, Robert Emile-Geay, Julien Noone, David C. Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
author_facet |
Singh, Hansi K. A. Hakim, Gregory J. Tardif, Robert Emile-Geay, Julien Noone, David C. |
author_sort |
Singh, Hansi K. A. |
title |
Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
title_short |
Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
title_full |
Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
title_fullStr |
Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
title_full_unstemmed |
Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework |
title_sort |
insights into atlantic multidecadal variability using the last millennium reanalysis framework |
publishDate |
2019 |
url |
https://doi.org/10.5194/cp-14-157-2018 https://cp.copernicus.org/articles/14/157/2018/ |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
albedo Arctic Greenland Iceland Sea ice |
genre_facet |
albedo Arctic Greenland Iceland Sea ice |
op_source |
eISSN: 1814-9332 |
op_relation |
doi:10.5194/cp-14-157-2018 https://cp.copernicus.org/articles/14/157/2018/ |
op_doi |
https://doi.org/10.5194/cp-14-157-2018 |
container_title |
Climate of the Past |
container_volume |
14 |
container_issue |
2 |
container_start_page |
157 |
op_container_end_page |
174 |
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1766249152565477376 |