Unprecedented springtime retreat of Antarctic sea ice in 2016

Abstract

During austral spring 2016 Antarctic sea ice extent (SIE) decreased at a record rate of 75 × 103 km2 d−1, which was 46% faster than the mean rate and 18% faster than in any previous spring season during the satellite era. The decrease of sea ice area was also exceptional and 28% greater than the mean. Anomalous negative retreat occurred in all sectors of the Antarctic but was greatest in the Weddell and Ross Seas. Record negative SIE anomalies for the day of year were recorded from 3 November 2016 to 9 April 2017. Rapid ice retreat in the Weddell Sea took place in strong northerly flow after an early maximum ice extent in late August. Rapid ice retreat occurred in November in the Ross Sea when surface pressure was at a record high level, with the Southern Annular Mode at its most negative for that month since 1968.

The Ross Sea Dipole – temperature, snow accumulation and sea ice variability in the Ross Sea region, Antarctica, over the past 2700 years

“…The recent change to a strongly negative SAM in November 2016 coincided with a significant reduction in Antarctic SIE, including the Ross Sea, during the 2016/17 summer (Turner et al, 2017). Longer observations are necessary to assess whether this recent trend continues and indeed forces the reduced SIE, but it fuels questions on the potential acceleration of future environmental change in the Antarctic/Southern Ocean region.…”

“…No such pattern is observed for regional surface air temperature (SAT) (Marshall and Thompson, 2016), which might be masked by the influence of regional sea ice variability on local temperatures. The positive SAM has been shown to contribute at least partially to an increase in total Antarctic sea ice, while a negative SAM has been associated with a reduced sea ice (Ferreira et al, 2015;Holland et al, 2017;Bintanja et al, 2013;Kohyama and Hartmann, 2015;Turner et al, 2017). The future behaviour of the SAM over the next decades is a topic of active research due to the competing and seasonally biased influences of projected stratospheric ozone recovery and greenhouse gas emissions (Bracegirdle et al, 2014;Gillett and Fyfe, 2013;Thompson et al, 2011).…”

Moisture transport and Antarctic sea ice: Austral spring 2016 event

“…Turner et al (2017) considered the spatial differences of the SIE anomalies and their temporal change at regional level and they related the low SIE over the Antarctic region to the warm air advection and the strong negative values of SAM in November and December. Schlosser et al (2017) have shown that the rapid decrease in the sea 25 ice area and extent were associated with atmospheric flow patterns reminiscent to a positive zonal wave number 3 (ZW3) index.…”

“…Sea ice extent is defined as the total area of all satellite 25 pixels where the sea ice concentration equals or exceeds 15%. Following previous studies (Zwally et al, 2002;Turner et al, 2017), we examine the anomalies of the daily and monthly SIC and SIE for the Southern Ocean as a whole and for five separate sectors (Figure 1): the Ross Sea (RS) (160°E-130°W), Amundsen-Bellingshausen Sea (ABS) (130°W-60°W), Weddell Sea (WS) (60°W-20°E), Indian Ocean (IO) (20°E-90°E), and western Pacific Ocean (WPO) (90°E-160°E).…”

“…featuring negative sea ice extent anomalies from September 2016 until April 2017. This shift in the sea ice extent variability could be caused either by a potential change of the long term trend or by natural climate variability (Turner et al, 2017).…”