Comparison of direct measurements of sea ice thickness and snow height, CryoSat-2 observations and PIOMAS numerical estimates

Abstract

The paper presents the results of comparison of contact measurements of ice thicknesses and snow heights performed at the points of the hydrological stations of the “Transarktika-2019” expedition in April 2019 north of Franz-Josef Land archipelago, with altimetry observations of the Cryosat-2 satellite and numerical estimates of the PIOMAS (Pan-Arctic numerical Ice and Ocean Modeling system and data Assimilation). A significantly better correspondence is predictably shown between the variability of the ice thickness directly measured and observed using the CryoSat-2 satellite than that for the numerical PIOMAS system estimates. A trial correction of the algorithm for calculating the ice thickness by replacing the climatic values of the ice density, snow density and height with data from direct measurements also predictably improves the quality of calculating the ice thickness from satellite observations. The mean / route mean square differences obtained for ice thicknesses (+44/+96 cm for uncorrected and +30/+95 cm for corrected CryoSat-2 satellite, –14/+81 cm for PIOMAS system) and snow height (–4/+12 cm for CryoSat-2 satellite, –15/+12 cm for PIOMAS system) show the scale of uncertainty in estimating sea ice thickness and snow height for areas dominated by medium and thick first-year ice. An anomaly of the ice thicknesses observed during the expedition is given in comparison with the background characteristics based on historical ice charting data for 1970s — 1990s, earlier High-Arctic aircraft “Sever” expeditions during 1950s — 1970s and the stated remote observations and numerical estimates for 2000s — 2019. Comparison shows that the AARI expedition was actually carried out in one of the most favorable years for ice research in the last decade for this region — the average ice thickness in April 2019 was 15 — 28 cm higher than that for the interval 2011 — 2019 with a slightly lower (1 — 2 cm) height of the snow cover. In the earlier period of the 1970 — 1990s this area was characterized by significantly thicker old ice with characteristic thicknesses ~ 60 cm more than in April 2019.