Combined remote and in situ study of sea ice thickness and motion in the Fram Strait

The CORESAT project: "Combined remote and in situ study of sea ice thickness and motion in the Fram Strait" improved our understanding of the sea ice thickness and sea ice drift distribution in the Fram Strait region and around Svalbard, which have a high impact on the local Arctic and global climate. A combination of satellite, airborne, and field data is used to achieve this goal. A short summary and activities of the project are published on the CORESAT website: http://www.npolar.no/en/projects/details?pid=2dd62226-e916-5f38-bb30-1df510f5aac1 The project started in June 2013 and lasted until summer 2017; it had seven partners, three from Norway (NPI, UiT, NERSC), three from Germany (AWI, Univ. Hamburg, Univ. Bremen), and one from Canada (York University). A postdoctoral researcher was hired for 3 years starting September 2013. A successful kick-off meeting was held on 5-6 October 2013 at the Norwegian Polar Institute, Tromsø: http://www.npolar.no/en/news/2013/2013-09-10-kick-off.html Over the project progress was made both on the field data and satellite data side. Among other things, sea ice thickness data from Fram Strait were processed, compiled, and published. All helicopter-borne ice thickness measurements with coincident satellite observations were processed. All helicopter-borne ice thickness information for the Barents Sea was processed and published in Journal of Geophysical Research. A publication with a first comparison of, amongst other things, helicopter-borne ice thickness measurements to SMOS thin sea ice thickness was published in Remote Sensing of Environment. Monthly ice thickness data from CryoSat is available and was preliminary compared to Upward Looking Sonar (ULS) data. Processing of individual CryoSat orbits with correspondent airborne ice thickness data was made. A SAR sea ice drift tracking algorithm was applied to a one month time series of Radarsat-2 SAR scenes in Fram Strait and to selected scenes north of Svalbard. A comparison to a lower resolution microwave radiometer sea ice drift dataset was made. A sea ice volume export time series combining the low resolution satellite ice drift data and ULS data was constructed. From the project, so far 13 peer review articles were published (3 of those after the regular final project reporting), and several more are submitted or in preparation.

The project will improve our understanding of the sea ice thickness and sea ice drift distribution in the Fram Strait region, which has a high impact on the local Arctic and global climate. While satellite observations of the sea ice extent exist since t he 1970, satellite observations of the sea ice thickness are a new development starting only at the beginning of this century. Existing methods to derive Arctic sea ice thickness and motion from satellite data were developed and validated mainly in the ce ntral Arctic Basin. However, the main gateway where sea ice leaves the Arctic Basin (~90%) is the Fram Strait. An accurate estimate of the Fram Strait sea ice volume export is needed to understand the recent Arctic sea ice decline (discrimination between thermodynamic (increased warming) and dynamic (increased export) forcing) as well as the influence on the ocean dense water formation and thereby the global thermohaline circulation. This project will exploit the comprehensive and worldwide unique in sit u sea ice observation database at the Norwegian Polar Institute and partner institutes to improve our understanding of sea ice remote sensing data. Established (ICESat ice freeboard/thickness, low-resolution radiometer/scatterometer ice drift) and new (Cr yoSat-2 ice freeboard/thickness, SAR ice drift, SMOS thin ice thickness) sea ice remote sensing datasets will be compared and evaluated against available in situ measurements obtained from ship, ice station, and helicopter surveys. When necessary, availab le remote sensing methods will be improved (ICESat, CryoSat-2) or newly developed (sea ice drift tracking from polarimetric SAR) specifically for the very dynamic and complex sea ice pack situation in Fram Strait.