[A-CG47] Status and future view on global ocean observation: toward achievement and development for OneArgo

[ACG47-P01] Performance of Ice Sensing Algorithms for Argo Floats in Southern Ocean

*Taiyo Kobayashi¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:Polar Argo, under-ice measurement, ice sensing algorithm, Southern Ocean

This study evaluated the performance of the ice sensing algorithms (ISAs) used for Argo floats in the Southern Ocean with the hydrographic profiles observed by Argo and marine mammals and the sea ice concentration (SIC) measured by satellite. There are numerous positionless Argo profiles, the SICs of which were obtained statistically. This study clarified that the existing ISAs have almost the same efficacy for ice avoidance. However, the performance of ISAs with the default setting was lower than the expected performance; for example, Klatt et al.’s ISA, which was first introduced to Argo floats, fails to detect sea ice with a probability of 37.5% and allows a float to ascend to the icy surface with a SIC of up to about 80% on average. Therefore, we strongly suggest that the critical temperature (Tcrit) for decision-making be changed to about -1.5°C, at which the failure rate for sea ice detection decreases to less than 10% and the average SIC where the float is allowed to ascend decreases to less than about 25%. A warmer setting of Tcrit > about -1.5°C causes a fatal problem in which the ISA may not allow a float to ascend to the sea surface throughout the year, especially in the Weddell and Ross Seas