Applicant

Dr. Gunnar Spreen
Universität Bremen
Institut für Umweltphysik
Abteilung für Erdfernerkundung
Otto-Hahn-Allee 1
28359 Bremen

Project Description

Sea ice is one of the Earth's climate components exhibiting the greatest change during the last decades. For example, sea ice controls the energy and gas fluxes between ocean and atmosphere in polar regions. Due to its high albedo it efficiently reflects shortwave radiation back to space, and affects the ecosystem. While the sea ice area in the Arctic is rapidly decreasing with a rate of about -4%/decade the sea ice area in the Antarctic is slowly increasing (about 1.5%/decade). Especially pronounced is the decrease in thick, multiyear sea ice in the Arctic with a rate of about -13%/decade. The area of multiyear sea ice in the Arctic can be determined from microwave satellite observations. In the Antarctic the area of perennial ice, i.e. sea ice surviving the summer melt, is smaller than in the Arctic, however, with 3 million square kilometres still quite significant. No method exists today to monitor the distribution and temporal development of perennial ice in the Antarctic throughout the season or on decadal time scales. Here we propose to develop a method to observe Antarctic sea ice types, especially perennial ice, from microwave satellite observations.Due to a decrease in salinity after the summer melt the dielectric properties and porosity of the perennial sea ice change, which makes it possible to distinguish from other ice types by active and passive microwave sensors. In the Antarctic the high snow load, which can cause ice flooding, snow melt-refreeze cycles, and sea ice dynamics in the marginal ice zone (leading to increasing ridging, smaller floes, pancake ice) makes the discrimination of sea ice types, e.g. separation of perennial from seasonal ice more challenging. Recently methods were developed to mitigate such influences leading to false ice type classification for the Arctic. We propose here to adapt and extend an ice type retrieval algorithm, which has been applied at the University of Bremen to Arctic sea ice, including two correction schemes for mitigating false classifications to the conditions of Antarctic sea ice. The proposed method relies on combined microwave radiometer and scatterometer observations for the ice type discrimination and on satellite derived sea ice drift and atmospheric reanalysis for the ice type classification correction. The outcome will be the first circumpolar, long-term time series of Antarctic sea ice types (perennial and seasonal ice, and potentially also young ice).

DFG Programme: Infrastructure Priority Programmes

International Connection: Canada

Cooperation partners: Mohammed Shokr, Ph.D.; Dr. Yufang Ye

Co-Applicants: Dr. Stefan Hendricks; Dr. Stefan Kern

Term since 2017