Gravity of the Arctic Ocean from satellite data with validations using airborne gravimetry: Oceanographic implications

Abstract

Precise mappings of sea surface topography, slope, and gravity of the Arctic Ocean are derived from altimeter data collected by Envisat and ICESat. Both altimeters measured instantaneous sea surface height at leads in the sea ice. To reduce contamination by ice‐freeboard signal and tracker noise in Envisat height data, a retracking of the waveform data was performed. Analogous reprocessing of ICESat data was also done. Arctic mean sea surfaces (MSSs) were computed from Envisat data spanning 2002–2008 and ICESat data spanning 2003–2009. Farrell et al. (2012) used these “ICEn” MSSs to estimate mean dynamic topography (MDT). These same Envisat and ICESat data are used, in sea‐surface‐slope form, to compute the ARCtic Satellite‐only (ARCS‐2) altimetric marine gravity field. ARCS‐2 extends north to 86°N and uses GRACE/GOCE gravity data (GOCO02S) for its long‐wavelength (>260 km) components. Use of Envisat data improves the spatial resolution over that of existing Arctic marine gravity fields in many areas. ARCS‐2's spatial resolution aids in tracing tectonic fabric—e.g., extinct plate boundaries—over broad areas of the Arctic basin whose tectonic origin remains a mystery. ARCS‐2's precision is validated using NASA 2010/2011 Operation IceBridge (OIB) airborne gravimetry. ARCS‐2 and OIB gravity along with ICEn‐MSS results are employed to locate short‐wavelength errors approaching 1 m in current Arctic marine geoids (EGM2008). Precise OIB airborne gravity corroborates that such errors in current geoid/gravity models are widespread in Arctic areas lacking accurate surface gravity data. These geoid errors limit the spatial resolution at which MDT can be mapped.