Abstract
AbstractThis 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.
Highlights
The loss of Arctic sea ice since the late 1970s has been observed by routine satellite missions (Stroeve and Notz 2018)
April– May (AM) sea ice concentration (SIC) anomalies regressed onto SO(21) dipole sea ice index show large positive SIC anomalies in the Barents Sea (BS) (Fig. 1c), confirming that springtime BS SIC anomalies relate to preceding autumn sea ice dipole anomalies
We find very similar temporal evolutions of the two sea ice indices during 1980–2016 (Fig. 1d) and their correlation is as high as 0.71, indicating that ;50% of BS sea ice variability can be explained by the SO(21) sea ice dipole variability
Summary
The loss of Arctic sea ice since the late 1970s has been observed by routine satellite missions (Stroeve and Notz 2018). On top of the apparent decreasing trend, the Arctic sea ice exhibits strong natural variability (Kay et al 2011; Notz and Marotzke 2012; Stroeve et al 2012). Multiple mechanisms have been investigated to understand the origin of the sea ice variability. Some studies attributed it to atmospheric dynamical and radiative drivers (e.g., Kay et al 2008; Graversen et al 2011; Herbaut et al 2015; Urrego-Blanco et al 2019), while others emphasized the roles of oceanic and sea ice processes (e.g., Shimada et al 2006; Yeager et al 2015; Zhang 2015; Årthun et al 2017; Oldenburg et al 2018) and their interactions (e.g., Nakanowatari et al 2014; Krikken and Hazeleger 2015). The interplay of natural variability and decreasing trend leads to spatial heterogeneity of the sea ice variability (Close et al 2015; Zhang 2015; Lee et al 2017; Onarheim and Årthun 2017)
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