New geoid of Greenland: A case study of terrain and ice effects, GOCE and use of local sea level data

• Main Authors: Forsberg, René, Jensen, Tim Enzlberger
• Other Authors: , Shuanggen Jin, Riccardo Barzaghi
• Format: Other Non-Article Part of Journal/Newspaper
• Language: English
• Published: Springer 2015
• Subjects: Geoid; Gravity; Greenland; Ice Sheet; Iceland; Sea ice
• Online Access: https://orbit.dtu.dk/en/publications/a2b45339-35e6-4d4f-85d3-5c8c56aea329; https://doi.org/10.1007/1345_2015_50

Making an accurate geoid model of Greenland has always been a challenge due to the ice sheet and glaciers, and the rough topography and deep fjords in the ice free parts. Terrestrial gravity coverage has for the same reasons been relatively sparse, with an older airborne survey of the interior being the only gravity field data over the interior, and terrain and ice thickness models being insufficient both in terms of resolution and accuracy. This data situation has in the later years changed substantially, first of all due to GOCE, but also new airborne gravity and ice thickness data from the NASA IceBridge mission, and new terrain models from ASTER, SPOT-5 and digital photogrammetry. In the paper we use all available data to make a new geoid of Greenland and surrounding ocean regions, using remove-restore techniques for ice and topography, spherical FFT techniques and downward continuation by least squares collocation. The impact of GOCE and the new terrestrial data yielded a much improved geoid, as evidenced by comparison to GPS measurements along fjords, which serves as a proxy for GPS leveling data, and comparisons to new GPS leveling data in Iceland. The comparisons show significant improvements over EGM08 and older geoid models, and also highlight the problems of global sea level models, especially in sea ice covered regions, and the definition of a new consistent vertical datum of Greenland.