Meltwater lenses over the Chukchi and the Beaufort seas during summer
2019: from in-situ to synoptic view.
Abstract
We investigate the Chukchi and the Beaufort seas, where salty and warm
Pacific Water flows in from the Bering Strait and interacts with the sea
ice, contributing to its summer melt. For the first time, thanks to
in-situ measurements recorded by two saildrones deployed during summer
2019 and to refined sea ice filtering in satellite L-Band radiometric
data, we demonstrate the ability of satellite Sea Surface Salinity (SSS)
observed by SMOS and SMAP to capture SSS freshening induced by sea ice
melt, referred to as meltwater lenses (MWL). The largest MWL observed by
the saildrones during this period occupied a large part of the Chukchi
shelf, with a SSS freshening reaching -5 pss. it persisted for up to one
month, to this MWL, induced low SSS pattern which restricted the
transfer of air-sea momentum to the upper, as illustrated by measured
wind speed and vertical profiles of currents. Combined with
satellite-based Sea Surface Temperature, satellite SSS provides a
monitoring of the different water masses encountered in the region
during summer 2019. Using sea ice concentration and estimated Ekman
transport, we analyse the spatial variability of sea surface properties
after the sea ice edge retreat over the Chukchi and the Beaufort seas.
The two MWL captured by both, the saildrones and the satellite
measurements, result from different dynamics. Over the Beaufort Sea, the
MWL evolution follows the meridional sea ice retreat, whereas in the
Chukchi Sea, a large persisting MWL is generated by advection of a sea
ice filament.