Regional variability of Arctic sea ice seasonal change climate indicators from a passive microwave climate data record

Abstract

The seasonal evolution of Arctic sea ice can be described by the timing of key dates of sea ice concentration (SIC) change during its annual retreat and advance cycle. Here, we use SICs from a satellite passive microwave climate data record to identify the sea ice dates of opening (DOO), retreat (DOR), advance (DOA), and closing (DOC) and the periods of time between these events. Regional variability in these key dates, periods, and sea ice melt onset and freeze-up dates for 12 Arctic regions during the melt seasons of 1979-2016 is investigated. We find statistically significant positive trends in the length of the melt season (outer ice-free period) for most of the eastern Arctic, the Bering Sea, and Hudson and Baffin Bays with trends as large as 11.9 d decade −1 observed in the Kara Sea. Trends in the DOR and DOA contribute to statistically significant increases in the length of the open water period for all regions within the Arctic Ocean ranging from 3.9 to 13.8 d decade −1 . The length of the ice retreat period (DOR−DOO) ranges from 17.1 d in the Sea of Okhotsk to 41 d in the Greenland Sea. The length of the ice advance period (DOC−DOA) is generally much shorter and ranges from 17.9 to 25.3 d in the Sea of Okhotsk and Greenland Sea, respectively. Additionally, we derive the extent of the seasonal ice zone (SIZ) and find statistically significant negative trends (SIZ is shrinking) in the Sea of Okhotsk, Baffin Bay, Greenland Sea, and Barents Sea regions, which are geographically open to the oceans and influenced by reduced winter sea ice extent. Within regions of the Arctic Ocean, statistically significant positive trends indicate that the extent of the SIZ is expanding as Arctic summer sea ice declines.

Seasonal transition dates can reveal biases in Arctic sea ice simulations

“…The open water period, also known as the inner ice-free period (Bliss et al, 2019), is defined as the number of days between ice break-up and freeze-up (also commonly referred to as ice retreat and advance). The open water period has been utilized as a metric to study variability and trends in the sea ice (Serreze et al, 2016;Barnhart et al, 2016) and seasonal predictability of the ice (Stroeve et al, 2016).…”

“…Using this rich data set, we evaluate model biases in the context of both the observed sea ice state and multiple simulated representations of internal variability. freeze-up and advance have been defined using ice concentration data in satellite data (Stammerjohn et al, 2012;Serreze et al, 2016;Stroeve et al, 2016;Bliss et al, 2019) and in model studies (Barnhart et al, 2016;Wang et al, 2018). However, these studies are often difficult to compare directly, since the definitions themselves vary substantially in terms of the region and date range studied, the selected threshold of ice concentration and the criteria that the threshold must meet (e.g.…”

“…Break-up is defined as the last day that sea ice concentration passes below the threshold of 15% between March 1 and the annual sea ice concentration minimum date (Bliss et al, 2019). Freeze-up is defined as the first day that sea ice concentration passes above the 15% threshold between the sea ice concentration minimum date and February 28 of the following year.…”

Multi-scale observations of the co-evolution of sea ice thermophysical properties and microwave brightness temperatures during the summer melt period in Hudson Bay

“…Hudson Bay is a large inland sea that experiences a full melt and refreeze of sea ice during the annual cycle, resulting in the Bay being comprised predominantly of first year sea ice during the winter (Hochheim and Barber, 2014). The seasonality of sea ice is changing in Hudson Bay, with ice breakup occurring earlier and freeze-up occurring later in the year (Hochheim and Barber, 2014;Bliss et al, 2019). Various studies have assessed the change in the timing of sea ice formation/breakup (Gough et al, 2004;Gagnon and Gough, 2005;Hochheim and Barber, 2014;Bliss et al, 2019), being a metric of particular importance to shipping and maritime activities within the bay (Andrews et al, 2017).…”

“…The seasonality of sea ice is changing in Hudson Bay, with ice breakup occurring earlier and freeze-up occurring later in the year (Hochheim and Barber, 2014;Bliss et al, 2019). Various studies have assessed the change in the timing of sea ice formation/breakup (Gough et al, 2004;Gagnon and Gough, 2005;Hochheim and Barber, 2014;Bliss et al, 2019), being a metric of particular importance to shipping and maritime activities within the bay (Andrews et al, 2017). Despite Hudson Bay being an area of importance to the livelihoods of local communities, and a potential major shipping and tourism route for the Canadian prairie provinces (Dawson et al, 2016), few studies examining the passive microwave signature of Hudson Bay sea ice exist, particularly during the summer melt period.…”