Sea Ice Meltwater in the Beaufort Gyre: A Comprehensive Analysis Using Sea Surface Salinity Data From SMOS

Arctic sea ice is retreating. In the Beaufort Gyre (BG), liquid freshwater content (FWC) has increased by 40% in the last two decades, with sea ice melting being one of the contributors. Combining satellite observations and reanalysis outputs, we study the sea ice meltwaters in the BG from 2011 to 2019. SMOS sea surface salinity (SSS) data were limited to the ice-free period, and reanalysis outputs showed limited accuracy in capturing the postmelt freshening observed in SMOS SSS. Applying criteria of SSS 25 psu and sea ice presence, we identified meltwater lenses (MWLs) across different years with higher frequency in 2011, 2015, and 2016, contrasting with scarcity in 2012, 2017, and 2019. MWLs showed lower SSS and temperature than river-influenced waters. Daily evolution of SSS and sea ice area within the MWLs exhibited similar patterns during both melting and formation stages. Furthermore, events of sea surface salinification following sea ice formation suggest that SMOS SSS might be capturing information on brine rejection. Atmospheric conditions suggested that the anticyclonic wind regime in 2011 contributed to meltwater retention, while the cyclonic wind pattern in 2016 favored outward meltwater dispersion. From our estimations, September's sea ice melting may contribute 10%–30% of the BG's annual FWC increase, though our method likely underestimates meltwater volume due to unaccounted advection processes. This study provides a validated method for MWL detection and underscores the importance of monitoring sea ice meltwaters to better understand regional variability in the BG within a changing climate.