The importance of North Atlantic Ocean transports for seasonal forecasts
Abstract The Atlantic Meridional Overturning Circulation (AMOC) is a main driver for predictability at decadal time scales, but has been largely ignored in the context of seasonal forecasts. Here, we show compelling evidence that AMOC initialization can have a direct and strong impact on seasonal fo...
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crspringernat:10.1007/s00382-020-05364-6 2023-05-15T17:29:47+02:00 The importance of North Atlantic Ocean transports for seasonal forecasts Tietsche, Steffen Balmaseda, Magdalena Zuo, Hao Roberts, Christopher Mayer, Michael Ferranti, Laura 2020 http://dx.doi.org/10.1007/s00382-020-05364-6 https://link.springer.com/content/pdf/10.1007/s00382-020-05364-6.pdf https://link.springer.com/article/10.1007/s00382-020-05364-6/fulltext.html en eng Springer Science and Business Media LLC https://creativecommons.org/licenses/by/4.0 https://creativecommons.org/licenses/by/4.0 CC-BY Climate Dynamics volume 55, issue 7-8, page 1995-2011 ISSN 0930-7575 1432-0894 Atmospheric Science journal-article 2020 crspringernat https://doi.org/10.1007/s00382-020-05364-6 2022-01-04T15:12:07Z Abstract The Atlantic Meridional Overturning Circulation (AMOC) is a main driver for predictability at decadal time scales, but has been largely ignored in the context of seasonal forecasts. Here, we show compelling evidence that AMOC initialization can have a direct and strong impact on seasonal forecasts. Winter reforecasts with SEAS5, the current operational seasonal forecasting system by the European Centre for Medium-Range Weather Forecasts, exhibit errors of sea-surface temperature (SST) in the western part of the North Atlantic Subpolar Gyre that are strongly correlated with decadal variations in the AMOC initial conditions. In the early reforecast period 1981–1996, too warm SST coincide with an overly strong AMOC transporting excessive heat into the region. In the ocean reanalyses providing the forecast initial conditions, excessive heat transport is balanced by additional surface cooling from relaxing towards observed SST, and therefore the fit to observations is acceptable. However, the additional surface cooling contributes to enhanced deep convection and strengthens the AMOC, thereby establishing a feedback loop. In the forecasts, where the SST relaxation is absent, the balance is disrupted, and fast growth of SST errors ensues. The warm SST bias has a strong local impact on surface air temperature, mean sea-level pressure, and precipitation patterns, but remote impact is small. In the late reforecast period 2001–2016, neither the SST in the western North Atlantic nor the AMOC show large biases. The non-stationarity of the bias prevents an effective forecast calibration and causes an apparent loss of skill in the affected region. The case presented here demonstrates the importance of correctly initializing slowly varying aspects of the Earth System such as the AMOC in order to improve forecasts on seasonal and shorter time scales. Article in Journal/Newspaper North Atlantic Springer Nature (via Crossref) Climate Dynamics 55 7-8 1995 2011 |
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Springer Nature (via Crossref) |
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crspringernat |
language |
English |
topic |
Atmospheric Science |
spellingShingle |
Atmospheric Science Tietsche, Steffen Balmaseda, Magdalena Zuo, Hao Roberts, Christopher Mayer, Michael Ferranti, Laura The importance of North Atlantic Ocean transports for seasonal forecasts |
topic_facet |
Atmospheric Science |
description |
Abstract The Atlantic Meridional Overturning Circulation (AMOC) is a main driver for predictability at decadal time scales, but has been largely ignored in the context of seasonal forecasts. Here, we show compelling evidence that AMOC initialization can have a direct and strong impact on seasonal forecasts. Winter reforecasts with SEAS5, the current operational seasonal forecasting system by the European Centre for Medium-Range Weather Forecasts, exhibit errors of sea-surface temperature (SST) in the western part of the North Atlantic Subpolar Gyre that are strongly correlated with decadal variations in the AMOC initial conditions. In the early reforecast period 1981–1996, too warm SST coincide with an overly strong AMOC transporting excessive heat into the region. In the ocean reanalyses providing the forecast initial conditions, excessive heat transport is balanced by additional surface cooling from relaxing towards observed SST, and therefore the fit to observations is acceptable. However, the additional surface cooling contributes to enhanced deep convection and strengthens the AMOC, thereby establishing a feedback loop. In the forecasts, where the SST relaxation is absent, the balance is disrupted, and fast growth of SST errors ensues. The warm SST bias has a strong local impact on surface air temperature, mean sea-level pressure, and precipitation patterns, but remote impact is small. In the late reforecast period 2001–2016, neither the SST in the western North Atlantic nor the AMOC show large biases. The non-stationarity of the bias prevents an effective forecast calibration and causes an apparent loss of skill in the affected region. The case presented here demonstrates the importance of correctly initializing slowly varying aspects of the Earth System such as the AMOC in order to improve forecasts on seasonal and shorter time scales. |
format |
Article in Journal/Newspaper |
author |
Tietsche, Steffen Balmaseda, Magdalena Zuo, Hao Roberts, Christopher Mayer, Michael Ferranti, Laura |
author_facet |
Tietsche, Steffen Balmaseda, Magdalena Zuo, Hao Roberts, Christopher Mayer, Michael Ferranti, Laura |
author_sort |
Tietsche, Steffen |
title |
The importance of North Atlantic Ocean transports for seasonal forecasts |
title_short |
The importance of North Atlantic Ocean transports for seasonal forecasts |
title_full |
The importance of North Atlantic Ocean transports for seasonal forecasts |
title_fullStr |
The importance of North Atlantic Ocean transports for seasonal forecasts |
title_full_unstemmed |
The importance of North Atlantic Ocean transports for seasonal forecasts |
title_sort |
importance of north atlantic ocean transports for seasonal forecasts |
publisher |
Springer Science and Business Media LLC |
publishDate |
2020 |
url |
http://dx.doi.org/10.1007/s00382-020-05364-6 https://link.springer.com/content/pdf/10.1007/s00382-020-05364-6.pdf https://link.springer.com/article/10.1007/s00382-020-05364-6/fulltext.html |
genre |
North Atlantic |
genre_facet |
North Atlantic |
op_source |
Climate Dynamics volume 55, issue 7-8, page 1995-2011 ISSN 0930-7575 1432-0894 |
op_rights |
https://creativecommons.org/licenses/by/4.0 https://creativecommons.org/licenses/by/4.0 |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.1007/s00382-020-05364-6 |
container_title |
Climate Dynamics |
container_volume |
55 |
container_issue |
7-8 |
container_start_page |
1995 |
op_container_end_page |
2011 |
_version_ |
1766124582953025536 |