New insights into the sea-ice system north of Svalbard - lessons from the N-ICE2015 drift experiment
Regionality in sea ice and snow conditions in the Arctic Ocean are often neglected. Recent work from the Norwegian young sea ICE (N-ICE2015) expedition in the area north of Svalbard, showcases how sea ice in this region is frequently affected by passing winter storms that affect the sea-ice system in a number of ways that are unique to this region. The oceanic conditions, especially with relatively shallow warm Atlantic water, also affects the sea-ice system and sets the region apart from other regions of the Arctic.
Despite the waters around Svalbard being fairly well studied, there are surprisingly little information from winter. Here we make a synthesis of the first comprehensive dataset of winter observations from the N-ICE2015 expedition that took place in a thin first and second year sea-ice regime in the ‘stormy’ Atlantic Sector. The multidisciplinary dataset includes atmosphere, snow, sea-ice, ocean, and ecosystem observations from a drifting ice station from winter to spring (Jan-Jun). We use these observations to illustrate the mechanisms through which winter storms affect the coupled Arctic sea-ice system.
These short-lived and episodic synoptic-scale events transport pulses of heat and moisture into the Arctic, which temporarily reduces radiative cooling and henceforth ice growth. Cumulative snowfall from each sequential storm acts to deepen the snow pack, being thicker than in other regions of the Arctic, which insulates the sea-ice and inhibits ice growth for the remaining winter season. In addition, strong winds fracture the ice cover, enhance ice drift and thus also increase ocean heat fluxes which also can reduce thermodynamic ice growth.
The heavy snow load induces flooding of the ice, and snow-ice formation, which likely is much more widespread in this part of the Arctic than elsewhere, due to combination of heavy snow fall and thinning of the sea ice cover. Flooding also induced phytoplankton growth at the bottom of the snow pack, which is a widespread phenomenon in the Antarctic, but might become more prevalent in the Arctic with thinning ice, especially in the Atlantic sector. In spring, the broken up ice pack and prevalence of leads in the region allowed enough light to penetrate to the ocean, to sustain an early under-ice phytoplankton bloom, despite average snow depths of the order of 0.3-0.5 m. Thus the legacy of Arctic winter storms for sea-ice and the ice-associated ecosystem in the Atlantic Sector lasts far beyond their short lifespan.
