Abstract Predictability of seasonal sea ice advance in the Chukchi Sea has been investigated in the context of ocean heat transport from the Bering Strait; however, the underlying physical processes have yet to be fully clarified. Using the Pan-Arctic Ice–Ocean Modeling and Assimilation System (PIOMAS) reanalysis product (1979–2016), we examined seasonal predictability of sea ice advance in early winter (November–December) and its source using canonical correlation analysis. It was found that 2-month leading (September–October) surface heat flux and ocean heat advection is the major predictor for interannual variability of sea ice advance. Surface heat flux is related to the atmospheric cooling process, which has influenced sea ice area in the southeastern Chukchi Sea particularly in the 1980s and 1990s. Anomalous surface heat flux is induced by strong northeasterly winds related to the east Pacific/North Pacific teleconnection pattern. Ocean heat advection, which is related to fluctuation of volume transport in the Bering Strait, leads to decrease in the sea ice area in the northwestern Chukchi Sea. Diagnostic analysis revealed that interannual variability of the Bering Strait volume transport is governed by arrested topographic waves (ATWs) forced by southeasterly wind stress along the shelf of the East Siberian Sea. The contribution of ocean heat flux to sea ice advance has increased since the 2000s; therefore, it is suggested that the major factor influencing interannual variability of sea ice advance in early winter has shifted from atmospheric cooling to ocean heat advection processes. Significance Statement Predictability of sea ice advance in the marginal Arctic seas in early winter is a crucial issue regarding future projections of the midlatitude winter climate and marine ecosystem. This study examined seasonal predictability of sea ice advance in the Chukchi Sea in early winter using a statistical technique and historical model simulation data. We identified that atmospheric cooling and ocean heat transport are the two main predictors of sea ice advance, and that the impact of the latter has become amplified since the 2000s. Our new finding suggests that the precise information on wind-driven ocean currents and temperatures is crucial for the skillful prediction of interannual variability of sea ice advance under present and future climatic regimes.
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Autumn Arctic Pacific Sea Ice Dipole as a Source of Predictability for Subsequent Spring Barents Sea Ice Condition
Abstract This study uses observational and reanalysis datasets in 1980–2016 to show a close connection between a boreal autumn sea ice dipole in the Arctic Pacific sector and sea ice anomalies in the Barents Sea (BS) during the following spring. The September–October Arctic Pacific sea ice dipole variations are highly correlated with the subsequent April–May BS sea ice variations ( r = 0.71). The strong connection between the regional sea ice variabilities across the Arctic uncovers a new source of predictability for spring BS sea ice prediction at 7-month lead time. A cross-validated linear regression prediction model using the Arctic Pacific sea ice dipole with 7-month lead time is demonstrated to have significant prediction skills with 0.54–0.85 anomaly correlation coefficients. The autumn sea ice dipole, manifested as sea ice retreat in the Beaufort and Chukchi Seas and expansion in the East Siberian and Laptev Seas, is primarily forced by preceding atmospheric shortwave anomalies from late spring to early autumn. The spring BS sea ice increases are mostly driven by an ocean-to-sea ice heat flux reduction in preceding months, associated with reduced horizontal ocean heat transport into the BS. The dynamical linkage between the two regional sea ice anomalies is suggested to involve positive stratospheric polar cap anomalies during autumn and winter, with its center slowly moving toward Greenland. The migration of the stratospheric anomalies is followed in midwinter by a negative North Atlantic Oscillation–like pattern in the troposphere, leading to reduced ocean heat transport into the BS and sea ice extent increase.
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- Award ID(s):
- 1736738
- NSF-PAR ID:
- 10310770
- Date Published:
- Journal Name:
- Journal of Climate
- Volume:
- 34
- Issue:
- 2
- ISSN:
- 0894-8755
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The Bering Strait oceanic heat transport influences seasonal sea ice retreat and advance in the Chukchi Sea. Monitored since 1990, it depends on water temperature and factors controlling the volume transport, assumed to be local winds in the strait and an oceanic pressure difference between the Pacific and Arctic oceans (the “pressure head”). Recent work suggests that variability in the pressure head, especially during summer, relates to the strength of the zonal wind in the East Siberian Sea that raises or drops sea surface height in this area via Ekman transport. We confirm that westward winds in the East Siberian Sea relate to a broader central Arctic pattern of high sea level pressure and note that anticyclonic winds over the central Arctic Ocean also favor low September sea ice extent for the Arctic as a whole by promoting ice convergence and positive temperature anomalies. Month‐to‐month persistence in the volume transport and atmospheric circulation patterns is low, but the period 1980–2017 had a significant summertime (June–August) trend toward higher sea level pressure over the central Arctic Ocean, favoring increased transports. Some recent large heat transports are associated with high water temperatures, consistent with persistence of open water in the Chukchi Sea into winter and early ice retreat in spring. The highest heat transport recorded, October 2016, resulted from high water temperatures and ideal wind conditions yielding a record‐high volume transport. November and December 2005, the only months with southward volume (and thus heat) transports, were associated with southward winds in the strait.
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null (Ed.)Abstract The timing of melt onset in the Arctic plays a key role in the evolution of sea ice throughout Spring, Summer and Autumn. A major catalyst of early melt onset is increased downwelling longwave radiation, associated with increased levels of moisture in the atmosphere. Determining the atmospheric moisture pathways that are tied to increased downwelling longwave radiation and melt onset is therefore of keen interest. We employed Self Organizing Maps (SOM) on the daily sea level pressure for the period 1979–2018 over the Arctic during the melt season (April–July) and identified distinct circulation patterns. Melt onset dates were mapped on to these SOM patterns. The dominant moisture transport to much of the Arctic is enabled by a broad low pressure region stretching over Siberia and a high pressure over northern North America and Greenland. This configuration, which is reminiscent of the North American-Eurasian Arctic dipole pattern, funnels moisture from lower latitudes and through the Bering and Chukchi Seas. Other leading patterns are variations of this which transport moisture from North America and the Atlantic to the Central Arctic and Canadian Arctic Archipelago. Our analysis further indicates that most of the early and late melt onset timings in the Arctic are strongly related to the strong and weak emergence of these preferred circulation patterns, respectively.more » « less
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Abstract Based on observational data analyses and idealized modeling experiments, we investigated the distinctive impacts of central Pacific (CP-) El Niño and eastern Pacific (EP-) El Niño on the Antarctic sea ice concentration (SIC) in austral spring (September to November). The tropical heat sources associated with EP-El Niño and the co-occurred positive phase of Indian Ocean Dipole (IOD) excite two branches of Rossby wave trains that propagate southeastward, causing an anomalous anticyclone over the eastern Ross-Amundsen-Bellingshausen Seas. Anomalous northerly (southerly) wind west (east) of the anomalous anticyclone favor poleward (offshore) movements of sea ice, resulting in a sea ice loss (growth) in the eastern Ross-Amundsen Seas (the Bellingshausen-Weddell Seas). Meanwhile, the anomalous northerly (southerly) wind also advected warmer and wetter (colder and drier) air into the eastern Ross-Amundsen Seas (the Bellingshausen-Weddell Seas), causing surface warming (cooling) through the enhanced (reduced) surface heat fluxes and thus contributing to the sea ice melting (growth). CP-El Niño, however, forces a Rossby wave train that generates an anomalous anticyclone in the eastern Ross-Amundsen Seas, 20° west of that caused by EP-El Niño. Consequently, a positive SIC anomaly occurs in the Bellingshausen Sea. A dry version of the Princeton atmospheric general circulation model was applied to verify the roles of anomalous heating in the tropics. The result showed that EP-El Niño can remotely induce an anomalous anticyclone and associated dipole temperature pattern in the Antarctic region, whereas CP-El Niño generates a similar anticyclone pattern with its location shift westward by 20° in longitudes.more » « less
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Abstract The ongoing Arctic warming has been pronounced in winter and has been associated with an increase in downward longwave radiation. While previous studies have demonstrated that poleward moisture flux into the Arctic strengthens downward longwave radiation, less attention has been given to the impact of the accompanying increase in snowfall. Here, utilizing state-of-the-art sea ice models, we show that typical winter snowfall (snow water equivalent) anomalies of around 1.0 cm, accompanied by positive downward longwave radiation anomalies of ∼5 W m−2, can cause basinwide sea ice thinning by around 5 cm in the following spring over the Arctic seas in the Eurasian–Pacific seas. In extreme cases, this is followed by a shrinking of summer ice extent. In the winter of 2016/17, anomalously strong warm, moist air transport combined with ∼2.5-cm increase in snowfall (snow water equivalent) decreased spring ice thickness by ∼10 cm and decreased the following summer sea ice extent by 5%–30%. This study suggests that small changes in the pattern and volume of winter snowfall can strongly impact the sea ice thickness and extent in the following seasons.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1175/JCLI-D-20-0172.1
