Abstract
We present an analysis of Arctic sea ice topography using high resolution, three-dimensional, surface elevation data from the Airborne Topographic Mapper, flown as part of NASA's Operation IceBridge mission. Surface features in the sea ice cover are detected using a newly developed surface feature picking algorithm. We derive information regarding the height, volume and geometry of surface features from 2009-2014 within the Beaufort/Chukchi and Central Arctic regions. The results are delineated by ice type to estimate the topographic variability across first-year and multi-year ice regimes. The results demonstrate that Arctic sea ice topography exhibits significant spatial variability, mainly driven by the increased surface feature height and volume (per unit area) of the multi-year ice that dominates the Central Arctic region. The multi-year ice topography exhibits greater interannual variability compared to the first-year ice regimes, which dominates the total ice topography variability across both regions. The ice topography also shows a clear coastal dependency, with the feature height and volume increasing as a function of proximity to the nearest coastline, especially north of Greenland and the Canadian Archipelago. A strong correlation between ice topography and ice thickness (from the IceBridge sea ice product) is found, using a square-root relationship. The results allude to the importance of ice deformation variability in the total sea ice mass balance, and provide crucial information regarding the tail of the ice thickness distribution across the western Arctic. Future research priorities associated with this new dataset are presented and discussed, especially in relation to calculations of atmospheric form drag.
Highlights
Sea ice is a heterogeneous medium consisting of level and/or deformed ice floes of various spatial scales, separated by cracks and leads
The results demonstrate that Arctic sea ice topography exhibits significant spatial variability, mainly driven by the increased surface feature height and volume of the multi-year ice that dominates the Central Arctic region
The feature height increases towards the Beaufort Sea coastline in 2012, which coincides with a tongue of multi-year ice (MYI) that same year
Summary
Sea ice is a heterogeneous medium consisting of level and/or deformed ice floes of various spatial scales (hundreds of metres to several kilometres in diameter), separated by cracks and leads. We utilize recent, high-resolution data from the Airborne Topographic Mapper (ATM) laser altimeter, flown as part of NASA’s Operation IceBridge (OIB) mission (Krabill, 2013), to provide detailed information regarding the sea ice topography over a variety of Arctic sea ice regimes. Since 2011, OIB has operated a “narrow scan” ATM that features a lower across-track swath width of ∼ 45 m, increasing the shot density in the centre of the swath (Krabill, 2014) These narrow scan ATM data will be combined with the regular (“wide scan”) ATM data in specific case studies to assess the potential uncertainties in the surface feature detection from the lower mean spatial sampling of the wide scan ATM. We use the National Snow and Ice Data Center (NSIDC) regional mask of the Arctic Ocean and surrounding regions (http://nsidc.org/data/polar_stereo/tools_masks) (i) to ensure data are over sea ice, and (ii) to exclude regions (e.g. the Canadian Archipelago) from some of our analyses
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