Precursory Changes in Planetary Wave Activity for Midwinter Surface Pressure Anomalies over the Arctic

Takaya, Kazuhiko; Nakamura, Hisashi

doi:10.2151/jmsj.86.415

Cited by 20 publications

(19 citation statements)

References 32 publications

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“…Previous studies (e.g. Takaya and Nakamura, 2008; Nishii et al , 2011) suggested that an anticyclonic circulation over the B‐K Seas in late autumn and early winter affects the midwinter stratospheric circulation, weakening the intensity of the westerly zonal wind. As documented by Deser et al (2007), in midwinter the linear and nonlinear responses to sea‐ice reduction interact destructively, resulting in a zero near‐surface anomaly.…”

Section: Results From the Sensitivity Experimentsmentioning

confidence: 99%

“…The modified wave pattern consists of an intensified dipole of zonally asymmetric temperatures whose net effect is a stronger warm advection into the pole. This finding is consistent with the results of Takaya and Nakamura (2008). Kim et al (2014) and Sun et al (2015) also found that the upper‐level intensified heat flux associated with sea‐ice reduction in the Barents and Kara Seas was explained by modifications of a large‐wavenumber Z pattern in the upper troposphere.…”

Section: Discussionmentioning

confidence: 99%

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The transient atmospheric response to a reduction of sea‐ice cover in the Barents and Kara Seas

Ruggieri

Kucharski

Buizza

et al. 2017

Quart J Royal Meteoro Soc

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The observed reduction of Arctic sea-ice has drawn a lot of interest for its potential impact on mid-latitude weather variability. One of the outstanding challenges is to achieve a deeper understanding of the dynamical processes involved in this mechanism.To progress in this area, we have designed and performed an experiment with an intermediate complexity atmospheric model. The experiment shows a transient atmospheric response to a surface diabatic heating in the Barents and Kara seas leading to an anomalous circulation first locally, then over the polar region and finally over the Euro-Atlantic sector. A hypothesis that explains the mechanisms for the propagation of the signal is put forward. The discussion of this hypothesis provides an insight into the nature of the link between sea-ice forcing and the modes of internal variability of the atmosphere. We demonstrate that after removal of sea ice in the Barents and Kara seas, first the linear atmospheric response dominates and is confined in the proximity of the heating area, then a large-scale response, associated also to eddy-feedback, is found and finally anomalies reach the lower-stratosphere and show a hemispheric pattern in the troposphere. These results identify the drivers of the tropospheric connection between sea-ice variability and the North Atlantic Oscillation and highlight the role of the lower stratosphere.

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Section: Results From the Sensitivity Experimentsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The transient atmospheric response to a reduction of sea‐ice cover in the Barents and Kara Seas

Ruggieri

Kucharski

Buizza

et al. 2017

Quart J Royal Meteoro Soc

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“…Previous studies have also suggested stratospheric influence as a possible mechanism for the teleconnection between the variations in tropical SST and the NAO [ Scaife et al ., ; Cagnazzo and Manzini , ]. Takaya and Nakamura [] pointed out the importance of fluctuations of planetary waves in November to the annular mode in mid‐winter through modulation of the stratospheric polar vortex. It is thus not unrealistic to consider a possible link between sea‐ice reduction and the negative phase shift of the NAO in late winter via the stratospheric pathway.…”

Section: Discussionmentioning

confidence: 99%

A negative phase shift of the winter AO/NAO due to the recent Arctic sea‐ice reduction in late autumn

et al. 2015

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This paper examines the possible linkage between the recent reduction in Arctic sea-ice extent and the wintertime Arctic Oscillation (AO)/North Atlantic Oscillation (NAO). Observational analyses using the ERA interim reanalysis and merged Hadley/Optimum Interpolation Sea Surface Temperature data reveal that a reduced (increased) sea-ice area in November leads to more negative (positive) phases of the AO and NAO in early and late winter, respectively. We simulate the atmospheric response to observed sea-ice anomalies using a high-top atmospheric general circulation model (AGCM for Earth Simulator, AFES version 4.1). The results from the simulation reveal that the recent Arctic sea-ice reduction results in cold winters in mid-latitude continental regions, which are linked to an anomalous circulation pattern similar to the negative phase of AO/NAO with an increased frequency of large negative AO events by a factor of over two. Associated with this negative AO/NAO phase, cold air advection from the Arctic to the mid-latitudes increases. We found that the stationary Rossby wave response to the sea-ice reduction in the Barents Sea region induces this anomalous circulation. We also found a positive feedback mechanism resulting from the anomalous meridional circulation that cools the mid-latitudes and warms the Arctic, which adds an extra heating to the Arctic air column equivalent to about 60% of the direct surface heat release from the sea-ice reduction. The results from this high-top model experiment also suggested a critical role of the stratosphere in deepening the tropospheric annular mode and modulation of the NAO in mid to late winter through stratosphere-troposphere coupling.

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“…The anomaly reached the surface within a week, suggesting a downward coupling that might have contributed to the building of the subsequent major episode B3 that in turn amplified the sea ice deficit over the BKS. The above findings are consistent with Takaya and Nakamura () and Peings (), who showed that UB activity in November acts to increase the upward flux of planetary waves and thereby weaken the stratospheric vortex in December into January.…”

Section: Troposphere‐stratosphere Couplingmentioning

confidence: 99%

Ural Blocking Driving Extreme Arctic Sea Ice Loss, Cold Eurasia, and Stratospheric Vortex Weakening in Autumn and Early Winter 2016–2017

et al. 2019

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This study investigates the dynamics that led to the repeated cold surges over midlatitude Eurasia, exceptionally warm conditions and sea ice loss over the Arctic, and the unseasonable weakening of the stratospheric polar vortex in autumn and early winter 2016–2017. We use ERA‐Interim reanalysis data and COBE sea ice and sea surface temperature observational data to trace the dynamical pathways that caused these extreme phenomena. Following abnormally low sea ice conditions in early autumn over the Pacific sector of the Arctic basin, blocking anticyclones became dominant over Eurasia throughout autumn. Ural blocking (UB) activity was four times above climatological levels and organized in several successive events. UB episodes played a key role in the unprecedented sea ice loss observed in late autumn 2016 over the Barents‐Kara Seas and the weakening of the stratospheric vortex. Each blocking induced circulation anomalies that resulted in cold air advection to its south and warm advection to its north. The near‐surface warming anomalies over the Arctic and cooling anomalies over midlatitude Eurasia varied in phase with the life cycles of UB episodes. The sea ice cover minimum over the Barents‐Kara Seas in 2016 was not observed in late summer but rather in mid‐November and December shortly after the two strongest UB episodes. Each UB episode drove intense upward flux of wave activity that resulted in unseasonable weakening of the stratospheric vortex in November. The surface impact of this weakening can be linked to the migration of blocking activity and cold spells toward Europe in early winter 2017.

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Precursory Changes in Planetary Wave Activity for Midwinter Surface Pressure Anomalies over the Arctic

Cited by 20 publications

References 32 publications

The transient atmospheric response to a reduction of sea‐ice cover in the Barents and Kara Seas

The transient atmospheric response to a reduction of sea‐ice cover in the Barents and Kara Seas

A negative phase shift of the winter AO/NAO due to the recent Arctic sea‐ice reduction in late autumn

Ural Blocking Driving Extreme Arctic Sea Ice Loss, Cold Eurasia, and Stratospheric Vortex Weakening in Autumn and Early Winter 2016–2017

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