Tropical origin for the impacts of the Atlantic Multidecadal Variability on the Euro-Atlantic climate

Atlantic Multidecadal Variability (AMV) is known for influencing the mid-latitude climate variability, especially over the European region. This letter assesses the impact of the wintertime AMV in a group of 200-year atmospheric-only numerical experiments, in which the atmosphere is forced with posi...

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Bibliographic Details
Published in:Environmental Research Letters
Main Authors: Paolo Davini, Jost von Hardenberg, Susanna Corti
Format: Article in Journal/Newspaper
Language:English
Published: IOP Publishing 2015
Subjects:
Atlantic Multidecadal Variability (AMV)
Atmospheric blocking
North Atlantic Oscillation (NAO)
Global Climate Models
Environmental technology. Sanitary engineering
TD1-1066
Environmental sciences
GE1-350
Science
Q
Physics
QC1-999
North Atlantic
North Atlantic oscillation
Sea ice
Online Access:https://doi.org/10.1088/1748-9326/10/9/094010
https://doaj.org/article/9f22d0d00a19436193efcb5b3066eb46
Description
Summary:Atlantic Multidecadal Variability (AMV) is known for influencing the mid-latitude climate variability, especially over the European region. This letter assesses the impact of the wintertime AMV in a group of 200-year atmospheric-only numerical experiments, in which the atmosphere is forced with positive and negative AMV-like sea surface temperatures (SSTs) and sea ice concentration patterns. Anomalies are applied separately to the whole North Atlantic ocean, to the extratropics (north of 30° N) and to the tropics (between 0° and 30° N). Results show that AMV anomalies considerably affect the North Atlantic Oscillation (NAO), the jet stream variability and the frequency of atmospheric blocking over the Euro-Atlantic sector, resulting in a negative (positive) NAO during positive (negative) AMV. It is found that the bulk of the signal is originated in the tropics and it is associated with a Gill-like response—an anomalous upper tropospheric streamfunction dipole over the tropical Atlantic driven by the SST anomalies—and with the subsequent structural change of the upper-tropospheric jet, which affects the propagation of Rossby waves in the North Atlantic. Conversely, the NAO response is almost negligible when the AMV anomalies are applied only to the extratropics, suggesting that the relevance of SST anomalies along the North Atlantic frontal zone may be overestimated.

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