2002: The extra-strong warm winter event in North Asia and its accompanying anomalous atmospheric circulation

<p>The wintertime warm Arctic-cold Eurasia (WACE) temperature trend during 1990-2010 was characterized by accelerating warming in the Arctic region, cooling in Eurasia and accelerating autumn/winter Arctic sea ice loss. We identify two atmospheric circulation modes over the North Atlantic-Northern Eurasian sector which displayed strong upward trends over the same period and can explain a large part of the observed decadal WACE pattern. Both modes bear a close resemblance to well-known teleconnection patterns and are relatively independent from anomalies in Arctic sea-ice cover. The first mode (PC1) captures the recent negative trends in the North Atlantic Oscillation and increased Greenland blocking frequency while the second mode (PC2) is reminiscent of a Rossby wave train and reflects an increased blocking frequency over the Urals and North Asia. We find that the loss in the Arctic sea ice and the upward trends in the PC1/PC2 together account for most of the decadal Arctic warming trend (>80%). However, the decadal Eurasian cooling trends may be primarily ascribed to the two circulation modes alone: all of the cooling in Siberia is contributed to by the PC1, and 65% of the cooling in East Asia by their combination (the contribution by PC2 doubles that by PC1). Enhanced intraseasonal activity of the two circulation modes increases blocking frequencies over Greenland, the Ural region and North Asia, which drive anomalous moisture/heat flux towards the Arctic and alter the downward longwave radiation. It weakens warm advection and enhances advection of Arctic cold airmass towards Eurasia.</p>

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Two Leading Modes of Wintertime Atmospheric Circulation Drive the Recent Warm Arctic–Cold Eurasia Temperature Pattern

Journal of Climate ◽

10.1175/jcli-d-19-0403.1 ◽

2020 ◽

Vol 33 (13) ◽

pp. 5565-5587 ◽

Cited By ~ 1

Author(s):

Kunhui Ye ◽

Gabriele Messori

Keyword(s):

Sea Ice ◽

Atmospheric Circulation ◽

North Atlantic ◽

Arctic Sea Ice ◽

The Arctic ◽

The North ◽

Downward Longwave Radiation ◽

North Asia ◽

Arctic Sea ◽

The North Atlantic

AbstractThe wintertime warm Arctic–cold Eurasia (WACE) temperature trend during 1990–2010 was characterized by accelerating warming in the Arctic region, cooling in Eurasia, and accelerating autumn/winter Arctic sea ice loss. We identify two atmospheric circulation modes over the North Atlantic–northern Eurasian sector that displayed strong upward trends over the same period and can explain a large part of the observed decadal WACE pattern. Both modes bear a close resemblance to well-known teleconnection patterns and are relatively independent from variability in Arctic sea ice cover. The first mode (PC1) captures the recent negative trends in the North Atlantic Oscillation and increased Greenland blocking frequency, while the second mode (PC2) is reminiscent of a Rossby wave train and reflects an increased blocking frequency over the Urals and north Asia. We find that the loss in the Arctic sea ice and the upward trends in PC1 and PC2 together account for most of the decadal Arctic warming trend (>80%). However, the decadal Eurasian cooling trends may be primarily ascribed to the two circulation modes alone: all of the cooling in Siberia is contributed to by PC1 and 65% of the cooling in East Asia by their combination (the contribution by PC2 doubles that by PC1). Enhanced intraseasonal activity of the two circulation modes increases blocking frequencies over Greenland, the Ural region, and north Asia, which drive anomalous moisture/heat flux toward the Arctic and alter the downward longwave radiation. This also weakens warm advection and enhances advection of cold Arctic airmasses towards Eurasia.

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Arctic rapid sea ice loss events in regional coupled climate scenario experiments

Ocean Science ◽

10.5194/os-9-217-2013 ◽

2013 ◽

Vol 9 (2) ◽

pp. 217-248 ◽

Cited By ~ 19

Author(s):

R. Döscher ◽

T. Koenigk

Keyword(s):

Sea Ice ◽

Atmospheric Circulation ◽

Radiative Forcing ◽

Large Scale ◽

Climate Model ◽

Climate Scenario ◽

Clustering Of Events ◽

Event Clustering ◽

Anomalous Atmospheric Circulation ◽

Strong Control

Abstract. Rapid sea ice loss events (RILEs) in a mini-ensemble of regional Arctic coupled climate model scenario experiments are analyzed. Mechanisms of sudden ice loss are strongly related to atmospheric circulation conditions and preconditioning by sea ice thinning during the seasons and years before the event. Clustering of events in time suggests a strong control by large-scale atmospheric circulation. Anomalous atmospheric circulation is providing warm air anomalies of up to 5 K and is forcing ice flow, affecting winter ice growth. Even without a seasonal preconditioning during winter, ice drop events can be initiated by anomalous inflow of warm air during summer. It is shown that RILEs can be generated based on atmospheric circulation changes as a major driving force without major competing mechanisms, other than occasional longwave effects during spring and summer. Other anomalous seasonal radiative forcing or short-lived forcers (e.g., soot) play minor roles or no role at all in our model. RILEs initiated by ocean forcing do not occur in the model, although cannot be ruled out due to model limitations. Mechanisms found are qualitatively in line with observations of the 2007 RILE.

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Storylines of the 2018 Northern Hemisphere heat wave at pre-industrial and higher global warming levels

10.5194/esd-2019-91 ◽

2020 ◽

Author(s):

Kathrin Wehrli ◽

Mathias Hauser ◽

Sonia I. Seneviratne

Keyword(s):

Global Warming ◽

Atmospheric Circulation ◽

Northern Hemisphere ◽

System Model ◽

Boreal Summer ◽

Extreme Temperatures ◽

Atmospheric Circulation Patterns ◽

Circulation Patterns ◽

Anomalous Atmospheric Circulation ◽

Maximum Temperatures

Abstract. Extreme temperatures were experienced over a large part of the Northern Hemisphere during the 2018 boreal summer (hereafter referred to as NH2018 event), leading to major impacts to agriculture and society in the affected countries. Previous studies highlighted both the anomalous atmospheric circulation patterns during the event and the background warming due to human greenhouse gas emissions as main drivers for the event. In this study, we present Earth System Model experiments investigating different storylines of the NH2018 event given the same atmospheric circulation and alternative background global warming for: no human imprint, the 2018 conditions, and different mean global warming levels (1.5 °C, 2 °C, 3 °C, and 4 °C). The results reveal that the human-induced background warming was a strong contributor to the intensity of the NH2018 event, and that resulting extremes under similar atmospheric circulation conditions at higher levels of global warming would reach very dangerous levels. About 32 % (61 %) of the inhabited or agricultural area in the investigated region would reach maximum temperatures over 40 °C under 2 °C (4 °C) of global warming and similar atmospheric circulation conditions.

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