ICESat sea level comparisons

ICESat calculations of sea level and mesoscale variability are demonstrated and compared to calculations from TOPEX altimetry. In particular, we examine the accuracy of the ICESat Laser 2a Release 21 GLA15 ocean elevations. A global ICESat ocean elevation bias of -10.0 +/- 1.0 cm (low) was found with respect to TOPEX, obtained with a reference mean sea surface (MSS). Dual-satellite (ICESat - TOPEX) crossovers independently verify this bias, having a mean of -11.7 +/- 1.8 cm. The origin of this bias is unknown, although it may be related to sea state. Release 21 improvements have mitigated ICESat's thermally-induced day/night laser pointing variations to 1 to 2 cm in elevation. The average daily single-satellite internal crossover RMS is 12 cm for ICESat, 7 cm for TOPEX. ICESat laser altimetry is able to match TOPEX detection of major sea level anomaly and mesoscale variability features on a global scale.