Sea ice topography from NASA's Operation IceBridge and ICESat-2

Sea ice is a heterogenous medium composed of level ice floes of various sizes, pressure ridges and snow features. These features can obstruct fluid flow and contribute additional form drag on the ice, impact the formation of melt ponds over the ice surface (which can also contribute a form drag) and are also indicative of the ice strength. Altimetric measurements over sea ice are likely to be strongly influenced by variability in the sea ice topography, providing a potentially underestimated source of error in sea ice thickness assessments to-date.

NASA's Operation IceBridge airborne mission has profiled the spring (and occasionally fall/summer) Arctic sea ice pack since 2009 and sections of the western Antarctic sea ice pack in austral spring since 2009 (October/November, all years except 2015). The primary instrument on-board is the Airborne Topographic Mapper (ATM) laser altimeter, which provides a conical scan of the ice surface with laser footprints of ~1 m. NASA's new ICESat-2 laser altimetry satellite mission is also now providing continuous, very high-resolution, surface elevation data over the polar oceans, with along-track sampling of ~70 cm and footprints of ~15 m. Here we show the ice topography distribution from multiple years of Operation IceBridge data and recently collected ICESat-2 data. The ICESat-2 data benefit from near-complete monthly basin-scale coverage across both poles, however the IceBridge data benefit from higher spatial resolutions. Combining these data offer the potential to transform our understanding of the sea ice thickness distribution. We assess the functional forms of the ice topography distributions at basin-scales (e.g. Arctic/Southern Ocean) and section/swath-scales (hundreds of meters to kilometers) and explore the impact of footprint size on these topography distributions. We use classified coincident imagery to enable us to also process seasonal data (e.g. summer IceBridge campaigns) to assess the full seasonal variability in ice topography across the Arctic.