Over-wintering of Supraglacial Lakes on the Greenland Ice Sheet from Sentinel-1 and Landsat-8 Data

Abstract:

Supra-glacial lakes on the GrIS have become a focus of research relating to the contribution of the GrIS to sea level rise. Lakes have been observed to appear during the summer melt season. Though it appears that the quantity of water collected on the surface is small, it is thought that the fracture and drainage of these lakes delivers significant pulses of water to the ice sheet bed, influencing the dynamic movement of glaciers towards the sea. The pattern of this transport mechanism may be a central driver of its influence over dynamic losses, as the flow of the viscoelastic ice sheet will differ if the water is delivered in a short pulse or a slower constant supply. A number of studies have catalogued the traits of lakes with an aim to quantify lake areas, depths, and timing of formation and cessation using visible and near infrared remote sensing instruments mostly focused on the summer melt season. Little is known about the behaviour of the surface lakes over the winter. A recent examination of the over-wintering of surface lakes has been conducted by Koenig et al. [2015] using airborne radar. While the study is extensive in area covered, it is limited in its temporal resolution by the availability of Operation IceBridge data, typically at one pass per year. This study seeks to observe the development of lakes over the winter period. Sentinel-1A radar images are used to track the presence of surface lakes and their variation in three study sites on the Greenland ice sheet. The sites are as follows: upstream of Ryder glacier, upstream of Petermann glacier, and upstream of Jakobshavn glacier. Water masks are created based on summer Landsat-8 images following NDWI_ice  and then compared to Sentinel images at monthly temporal resolution through the winter of 2014-2015. These radar images show persistence of liquid water through the winter in agreement with previous research as well as variation in the buried lake area over the span of the year studied.