Trends and variability in polar sea ice, global atmospheric circulations, and baroclinicity

Simmonds, Ian; Li, Muyuan

doi:10.1111/nyas.14673

Cited by 83 publications

(44 citation statements)

References 157 publications

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“…We also note that regions experiencing positive fast-ice trends also coincide with regions experiencing trends toward higher sea-ice concentration. While the time periods of the Simmonds and Li (2021) paper differ to that presented here, we can indeed see that the general distribution of positive trend coincides with the Southern Hemisphere trend in concentration from 1979 to 2020 in September-November (Fig. 2b, bottom row of Simmonds and Li, 2021), but this link is somewhat less convincing for other seasons.…”

Section: Fast-ice Distribution Age and Trendscontrasting

confidence: 50%

“…While the time periods of the Simmonds and Li (2021) paper differ to that presented here, we can indeed see that the general distribution of positive trend coincides with the Southern Hemisphere trend in concentration from 1979 to 2020 in September-November (Fig. 2b, bottom row of Simmonds and Li, 2021), but this link is somewhat less convincing for other seasons. Nearby pack ice concentration is thought to buffer fast ice against wave-induced break-out (Crocker and Wadhams, 1989) and may also indicate that common environmental forcing is favourable for sea-ice formation/preservation.…”

Section: Fast-ice Distribution Age and Trendscontrasting

confidence: 50%

“…We also note that this is a region of increasing summertime, springtime and wintertime sea-ice concentration (Fig. 2 of Simmonds and Li, 2021), which may favour formation of more extensive or longer duration of fast-ice coverage; i.e. this fast-ice trend may be associated with an oceanic trend which has atmospheric drivers.…”

Section: Fast-ice Extent Anomalies and Linear Trendsmentioning

confidence: 89%

“…Fast-ice extent (10 3 km 2 ) Sea-ice extent (10 dicates that fast ice experiences a seasonal approximate 3fold increase in extent. As with overall sea ice (Eayrs et al, 2019;Parkinson, 2019;Simmonds and Li, 2021), fast ice displays an asymmetrical annual cycle, experiencing on average ∼ 7 months of advance and 5 months of retreat. As such, fast ice as a percentage of overall sea-ice area (extent) varies between a maximum of 12.8 % (8.5 %) in early-mid-February (coinciding with the overall sea-ice minimum in early-mid-February) and around 4.0 % (3.2 %) throughout the winter (mid-July to late November).…”

Section: Regionmentioning

confidence: 99%

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Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability

et al. 2021

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Abstract. Landfast sea ice (fast ice) is an important though poorly understood component of the cryosphere on the Antarctic continental shelf, where it plays a key role in atmosphere–ocean–ice-sheet interaction and coupled ecological and biogeochemical processes. Here, we present a first in-depth baseline analysis of variability and change in circum-Antarctic fast-ice distribution (including its relationship to bathymetry), based on a new high-resolution satellite-derived time series for the period 2000 to 2018. This reveals (a) an overall trend of -882±824 km2 yr−1 (-0.19±0.18 % yr−1) and (b) eight distinct regions in terms of fast-ice coverage and modes of formation. Of these, four exhibit positive trends over the 18-year period and four negative. Positive trends are seen in East Antarctica and in the Bellingshausen Sea, with this region claiming the largest positive trend of +1198±359 km2 yr−1 (+1.10±0.35 % yr−1). The four negative trends predominantly occur in West Antarctica, with the largest negative trend of -1206±277 km2 yr−1 (-1.78±0.41 % yr−1) occurring in the Victoria and Oates Land region in the western Ross Sea. All trends are significant. This new baseline analysis represents a significant advance in our knowledge of the current state of both the global cryosphere and the complex Antarctic coastal system, which are vulnerable to climate variability and change. It will also inform a wide range of other studies.

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Section: Fast-ice Distribution Age and Trendscontrasting

confidence: 50%

Section: Fast-ice Distribution Age and Trendscontrasting

confidence: 50%

Section: Fast-ice Extent Anomalies and Linear Trendsmentioning

confidence: 89%

Section: Regionmentioning

confidence: 99%

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Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability

et al. 2021

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“…Expanding Hadley cell (or poleward shift of the atmosphere circulation) ties to a systematic poleward shift of the mid-latitude eddy activity (Fig. 4e), which relates to a poleward shift of the baroclinicity (Yin 2005;Mbengue and Schneider 2018;Simmonds and Li 2021). Rudeva et al (2019) found that changes in mid-latitude frontal activity (strong temperature gradients) lead those in the edge of the Hadley cell by approximately one day.…”

Section: Discussionmentioning

confidence: 96%

Decoding the dynamics of poleward shifting climate zones using aqua-planet model simulations

Yang

Wang

et al. 2022

Clim Dyn

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Growing evidence indicates that the atmospheric and oceanic circulation experiences a systematic poleward shift in a warming climate. However, the complexity of the climate system, including the coupling between the ocean and the atmosphere, natural climate variability and land-sea distribution, tends to obfuscate the causal mechanism underlying the circulation shift. Here, using an idealised coupled aqua-planet model, we explore the mechanism of the shifting circulation, by isolating the contributing factors from the direct CO$$_2$$ 2 forcing, the indirect ocean surface warming, and the wind-stress feedback from the ocean dynamics. We find that, in contrast to the direct CO$$_2$$ 2 forcing, ocean surface warming, in particular an enhanced subtropical ocean warming, plays an important role in driving the circulation shift. This enhanced subtropical ocean warming emerges from the background Ekman convergence of surface anomalous heat in the absence of the ocean dynamical change. It expands the tropical warm water zone, causes a poleward shift of the mid-latitude temperature gradient, hence forces a corresponding shift in the atmospheric circulation and the associated wind pattern. The shift in wind, in turn drives a shift in the ocean circulation. Our simulations, despite being idealised, capture the main features of the observed climate changes, for example, the enhanced subtropical ocean warming, poleward shift of the patterns of near-surface wind, sea level pressure, storm tracks, precipitation and large-scale ocean circulation, implying that increase in greenhouse gas concentrations not only raises the temperature, but can also systematically shift the climate zones poleward.

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Winter anticyclone activities in Siberia and their relationship to the regional temperature anomaly

Chen

Zhang

Guan

2022

Intl Journal of Climatology

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Under global warming, the frequent occurrence of Eurasian extreme cold events in the Northern Hemisphere in recent years has attracted widespread attention. Winter Eurasia near-surface anticyclone activities are closely related to low temperatures. This study uses a new objective anticyclone identification algorithm based on a Mask region-based convolutional neural network (Mask R-CNN) to detect long-term winter Eurasian anticyclone activities. We found that most tracks of Eurasian anticyclones (30.5%) pass Siberia in winter. Anticyclone tracks over Siberia can be well separated into the eastward moving type, the northwest-southeast type, and the local type, with distinct associated circulation patterns. The energy dispersions of upstream Rossby waves have an important influence on the movement, maintenance and intensification of the three types. In association with anticyclones intensifying in Siberia, surface air temperatures in the mid-latitudes of Eurasia, especially Siberia, are significantly lower. In particular, the local type is the most active (56.1%) and is significantly correlated with the winter temperature anomaly in most areas of East Asia. Further research indicates that the preceding autumn sea ice condition in the Barents Sea can be used as a precursor factor to modulate the local type anticyclone activity and winter temperature anomaly in East Asia. In years of less ice, a quasi-meridional wave activity flux originating from the Barents Sea is more active, and the centre SLP of the local type anticyclone is higher with more cold air mass carried, which in turn results in colder weather in Siberia, the Mongolian Plateau and East Asia.

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Trends and variability in polar sea ice, global atmospheric circulations, and baroclinicity

Cited by 83 publications

References 157 publications

Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability

Eighteen-year record of circum-Antarctic landfast-sea-ice distribution allows detailed baseline characterisation and reveals trends and variability

Decoding the dynamics of poleward shifting climate zones using aqua-planet model simulations

Winter anticyclone activities in Siberia and their relationship to the regional temperature anomaly

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