Coastal polynyas: Winter oases for subadult southern elephant seals in East Antarctica

Abstract

Antarctic coastal polynyas are regions of persistent open water and are thought to be key bio-physical features within the sea-ice zone. However, their use by the upper trophic levels of ecosystems remains unclear. A unique bio-physical dataset recorded by southern elephant seals reveals that East Antarctic polynyas are a key winter foraging habitat for male seals. During their post-moult trips from Isles Kerguelen to the Antarctic continental shelf, a total of 18 out of 23 seals visited 9 different polynyas, spending on average 25 ± 20% (up to 75%) of their total trip time inside polynyas. Changes in seal foraging and diving behaviours are observed inside polynyas as compared to outside polynyas. Two polynya usages by seals are observed for the inactive and active polynya phases, pointing to different seasonal peaks in prey abundance. During the active polynya phase, we link seal foraging behaviour to changes in the physical stability of the water-column, which likely impact the seasonal biological dynamics within polynyas.

Recent Reoccurrence of Large Open‐Ocean Polynya on the Maud Rise Seamount

“…Open-ocean polynyas are regions of open water within the seasonal sea-ice cover, occurring away from the shore. The occurrence of such polynya is known to have consequence on the Antarctic bottom water properties (Zanowski et al, 2015), atmospheric circulation (Weijer et al, 2017), Antarctic marine ecosystem (Labrousse et al, 2018;Stirling, 1997), carbon uptake, and primary production (Arrigo & van Dijken, 2003;Shadwick et al, 2017). Understanding the interaction between the polynyas and overlaying atmosphere is crucial for assessing the role of high-latitude dynamics in global climate (Maqueda, 2004).…”

Movement responses to environment: fast inference of variation among southern elephant seals with a mixed effects model

“…Those animals whose forage migrations went towards the Antarctic continent showed low move persistence once in areas of higher sea ice coverage. Some individuals also showed positive responses to elevated chlorophyll a concentrations, targeting productive coastal polynya areas (Labrousse et al, 2018); however this was not a persistent response with many others foraging farther offshore in the marginal sea-ice zone where concentrations are lower (Appendix S4: Figure S1). This pattern might be suggestive of density-dependent habitat selection, whereby seals distribute themselves so that foraging success is consistent across habitats of differing value (Morris, 2011).…”

Trends in the Stability of Antarctic Coastal Polynyas and the Role of Topographic Forcing Factors

“…The adjusted record of changes in the extent of coastal polynyas and sea ice in the Southern Ocean indicate that there is a negative correlation between them.(the sea ice) [23,24]. The open waters of polynyas are also important habitats for birds and marine mammals [8,25,26].Depending on which mechanism forms and maintains polynyas in high latitude oceans, polynyas can be divided into open-ocean and coastal polynyas [1,7,27,28]. The formation of open-ocean polynyas is mainly due to a vertical circulation pattern, known as a "sensible-heat polynya" [1,27,29].…”

“…Due to the complexity of the influencing factors, the mechanisms behind the formation and maintenance of open-ocean polynyas are still not fully understood. The essence of a coastal polynya, in contrast, is a region where ice is constantly generated near the shore and is continuously carried out into the ocean by the action of local winds or ocean currents, which balances the loss of heat to the atmosphere and maintains the amount of heat in the open water at the same time [3,5,8,27,29,30]. The heat released into the atmosphere from coastal polynyas is derived from the heat that is lost from seawater in the form of "latent heat" during freezing.…”

“…(the sea ice) [23,24]. The open waters of polynyas are also important habitats for birds and marine mammals [8,25,26].…”