The refreezing of melt ponds on Arctic sea ice

Abstract

The presence of melt ponds on the surface of Arctic sea ice significantly reduces its albedo, inducing a positive feedback leading to sea ice thinning. While the role of melt ponds in enhancing the summer melt of sea ice is well known, their impact on suppressing winter freezing of sea ice has, hitherto, received less attention. Melt ponds freeze by forming an ice lid at the upper surface, which insulates them from the atmosphere and traps pond water between the underlying sea ice and the ice lid. The pond water is a store of latent heat, which is released during refreezing. Until a pond freezes completely, there can be minimal ice growth at the base of the underlying sea ice. In this work, we present a model of the refreezing of a melt pond that includes the heat and salt balances in the ice lid, trapped pond, and underlying sea ice. The model uses a two-stream radiation model to account for radiative scattering at phase boundaries. Simulations and related sensitivity studies suggest that trapped pond water may survive for over a month. We focus on the role that pond salinity has on delaying the refreezing process and retarding basal sea ice growth. We estimate that for a typical sea ice pond coverage in autumn, excluding the impact of trapped ponds in models overestimates ice growth by up to 265 million km 3 , an overestimate of 26%.

Wintertime storage of water in buried supraglacial lakes across the Greenland Ice Sheet

“…The formation of buried lakes on the GrIS follows the natural wintertime evolution of lake-ice formation observed over Arctic lakes on land, with similar ice thicknesses ranging between 1 and 2 m (e.g., Surdu et al, 2014). GrIS buried-lake formation also parallels melt pond refreezing on sea ice, wherein trapped ponds are created and persist until complete refreezing is accomplished (Flocco et al, 2015). Satellite images of the summertime extent of the supraglacial lakes paired with the subsurface radar data shown here suggest that at elevations above 1000 m all three types of supraglacial lakes coexist in the same region, all experiencing the same meteorological forcings.…”

Simultaneous disintegration of outlet glaciers in Porpoise Bay (Wilkes Land), East Antarctica, driven by sea ice break-up

“…This may have caused hydro-fracturing of pre-existing depressions in the landfast ice or surface thinning may have made it more vulnerable to fracturing through ocean swell or internal stresses. Additionally, the subsequent refreezing of some melt ponds may temporally inhibit basal ice growth, potentially weakening the multi-year sea ice and predisposing it to future breakup (Flocco et al, 2015). It is important to note that the atmospheric circulation anomalies which favoured the development of fractures in the multi-year sea ice in December 2005 were short-lived.…”

Arctic Ocean outflow and glacier–ocean interactions modify water over the Wandel Sea shelf (northeastern Greenland)

“…5) that appeared to be part of under-ice ponds (e.g. Eicken, 1994;Flocco et al, 2015) comprised of meltwater trapped in pockets below the multiyear landfast ice. This surface layer freshened during the melt season and was observed to have salinities of 1-8 during CTD transects in August 2015 (Bendtsen et al, 2017).…”