Summer Extreme Cyclone Impacts on Arctic Sea Ice

Abstract

In this study the impact of extreme cyclones on Arctic sea ice in summer is investigated. Examined in particular are relative thermodynamic and dynamic contributions to sea ice volume budgets in the vicinity of Arctic summer cyclones in 2012 and 2016. Results from this investigation illustrate sea ice loss in the vicinity of the cyclone trajectories during each year were associated with different dominant processes: thermodynamic (melting) in the Pacific sector of the Arctic in 2012, and both thermodynamic and dynamic processes in the Pacific sector of the Arctic in 2016. Comparison of both years further suggests that the Arctic minimum sea ice extent is influenced by not only the strength of the cyclone, but also by the timing and location relative to the sea ice edge. Located near the sea ice edge in early August in 2012, and over the central Arctic later in August in 2016, extreme cyclones contributed to comparable sea ice area (SIA) loss, yet enhanced sea ice volume loss in 2012 relative to 2016.Central to a characterization of extreme cyclone impacts on Arctic sea ice from the perspective of thermodynamic and dynamic processes, we present an index describing relative thermodynamic and dynamic contributions to sea ice volume changes. This index helps to quantify and improve our understanding of initial sea ice state and dynamical responses to cyclones in a rapidly warming Arctic, with implications for seasonal ice forecasting, marine navigation, coastal community infrastructure and designation of protected and ecologically sensitive marine zones.

Summer Cyclones and Their Association With Short-Term Sea Ice Variability in the Pacific Sector of the Arctic

“…This temporary shift to lower SIC may be an artifact of melt ponds being misclassified as open ocean (e.g., Meier et al, 2015), and this requires further investigation. Nonetheless, these apparent differences in the sea ice impacts of the two cyclones, despite their similar surface wind and energy forcing anomalies on sea ice, underscore the importance of the initial sea ice state and coupled upper ocean processes for determining the extent to which a cyclone impacts sea ice on short time scales (Lukovich et al, 2021).…”

“…Moreover, the distributional shift in SIC during the June cyclone is only temporary, as the SIC distribution begins to resemble the pre-cyclone distribution 2 days after the passage of the cyclone. These differences in the apparent sea ice impacts of two cyclones that have similar intensity and similar effects on the surface energy balance emphasize the importance of the initial sea ice state for anticipating how cyclones will affect sea ice on short time scales (Lukovich et al, 2021).…”

“…However, cyclones are likely having a larger effect on sea ice cover as young and thin sea ice becomes more widespread in the Arctic (Rampal et al, 2009;Maslanik et al, 2011;Spreen et al, 2011;Lindsay and Schweiger 2015;Itkin et al, 2017). Despite uncertainty in whether cyclones are a significant source of seasonal or interannual variability in pan-Arctic sea ice cover (Rae et al, 2017), numerous studies have demonstrated that cyclones are indeed a source of local and short term variability in sea ice cover and concentration (Zhang et al, 2013;Stern et al, 2020;Lukovich et al, 2021), and these shortterm changes in sea ice are critical for navigability within the Arctic region. This study examines how the surface winds and atmospheric energy flux from recent Arctic summer cyclones affects sea ice concentration on synoptic weather time scales of 1-10 days.…”

“…Whether the wind-induced advection of sea ice increases or decreases sea ice concentration at a given location, however, depends on the direction of the surface winds relative to the local gradient in ice concentration. Cyclonic surface winds enhance sea ice divergence, which locally reduces sea ice concentration in the vicinity of a cyclone (Maslanik and Barry 1989;Kriegsmann and Brümmer, 2014;Lukovich et al, 2021). In addition, strong surface winds later in the summer are increasingly capable of mixing relatively warm sub-surface sea water upward toward the surface, which causes substantial melting along the ocean-facing side of sea ice (Steele et al, 2010;Zhang et al, 2013;Stern et al, 2020).…”

“…Cyclone impacts on sea ice vary from case to case not only because of variability in the cyclones themselves, but also because of differences in the underlying sea ice cover. Lukovich et al (2021) compared the impacts of similarly intense Arctic cyclones in August 2012 and August 2016 on the sea ice. They found that the August 2012 cyclone had a more destructive effect on sea ice primarily because it affected thinner, lower-concentration sea ice than the August 2016 cyclone.…”