Robert Ricker, PhD
PhD project title: Thickness maps of Arctic and Antarctic sea ice and the effect of snow covered sea ice on radar altimeter measurements.
Sea ice thickness on basin-scale is an important variable in the polar climate system, however few datasets exists. Remote sensing satellites are the only possibility to accomplish that.
The 2010 launched CryoSat-2 satellite with its on-board Ku-Band radar altimeter (SIRAL) was especially developed for the observation of sea ice.
Radar altimeters measure their distance to the surface and with the knowledge of the sea level elevation one can receive the sea ice freeboard and finally its thickness under assumption of isostatic balance. Significant error sources for the freeboard-thickness conversion are the unknown physical properties of the snow layer, such as depth and density.
The objective of this thesis is to investigate the penetration of the radar waves into the snow and the effect of surface roughness. Therefore it is the goal to compare radar altimeter freeboard data with laser freeboard data and provide a forward model for the backscattered radar echo within a snow layer for a better understanding of the effect of a snow covered sea ice surface on radar altimeter measurements. The final goals are thickness maps of Arctic and Antarctic sea ice and their corresponding errors estimates.
Start of doctoral thesis: 01st July, 2011
Defence of doctoral thesis: 12th March, 2015 (view thesis)
Thesis committee members:
Supervisor. Prof. Rüdiger Gerdes
Co-supervisor: Dr. Stefan Hendricks
Further member: Dr. Veit Helm
Committee Meetings: 13.03.12
Programming languages: IDL, MATLAB, Python
Grosfeld, K. , Treffeisen, R. , Asseng, J. , Bartsch, A. , Bräuer, B. , Fritzsch, B. , Gerdes, R. , Hendricks, S. , Hiller, W. , Heygster, G. , Krumpen, T. , Lemke, P. , Melsheimer, C. , Nicolaus, M. , Ricker, R. and Weigelt, M. (2016): Online sea-ice knowledge and data platform <www.meereisportal.de> , Polarforschung, Bremerhaven, Alfred Wegener Institute for Polar and Marine Research & German Society of Polar Research, 85 (2), pp. 143-155 . doi: 10.2312/polfor.2016.011.
Schwegmann, S., Rinne, E., Ricker, R., Hendricks, S., and Helm, V.: About the consistency between Envisat and CryoSat-2 radar freeboard retrieval over Antarctic sea ice, The Cryosphere, 10, 1415-1425, doi:10.5194/tc-10-1415-2016, 2016.
Ricker, R.; Hendricks, S.; Beckers, J.F. The Impact of Geophysical Corrections on Sea-Ice Freeboard Retrieved from Satellite Altimetry. Remote Sens. 2016, 8, 317.
Ricker, R., S. Hendricks, D. K. Perovich, V. Helm, and R. Gerdes (2015), Impact of snow accumulation on CryoSat-2 range retrievals over Arctic sea ice: An observational approach with buoy data. Geophys. Res. Lett., 42, 4447–4455. doi: 10.1002/2015GL064081.
Price, D., Beckers, J., Ricker, R., Kurtz, N., Rack, W., Haas, C., ... & Langhorne, P. J. (2015). Evaluation of CryoSat-2 derived sea-ice freeboard over fast ice in McMurdo Sound, Antarctica. Journal of Glaciology, 61(226), 285-300.
Ricker, R., Hendricks, S., Helm, V., & Gerdes, R. (2015). Classification of CryoSat-2 radar echoes. In Towards an Interdisciplinary Approach in Earth System Science (pp. 149-158). Springer International Publishing.
Ricker, R., Hendricks, S., Helm, V., Skourup, H., and Davidson, M.: Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation, The Cryosphere, 8, 1607-1622, doi:10.5194/tc-8-1607-2014, 2014.
Conferences & Workshops:
2016 ESA Living Planet Symposium, Prague, Czech Republic, Talk.
2015 American Geophysical Union Fall Meeting, San Francisco, United States, Invited Talk.
2015 Sentinel-3 for Science Workshop, Venice, Italy, Poster.
2014 American Geophysical Union Fall Meeting, San Francisco, United States, Talk.
2014 International Symposium on Sea Ice in a Changing Environment, Hobart, Australia, Talk.
2013 Davos Atmosphere and Cryosphere Assembly, Davos, Switzerland, Talk.
2013 Lidar Measurements of the Cryosphere Workshop, Reykholt, Iceland, Talk.
2013 CryoSat Third User Workshop, Dresden, Germany, Poster.
2012 Earth Observation and Cryosphere Science Conference, Frascati, Italy, Talk.
2012 20 Years of Progress in Radar Altimetry, Venice, Italy, Poster.
Expeditions/ field work:
Polarstern expedition ARKXXVI/3 “TransArc“,Tromsø – Bremerhaven, 05 August – 07 October 2011
CryoVex 2011 Aircraft campaign, Longyearbyen, Spitzbergen, 25-29 March