Weddell Sea subsurface warming revealed by an updated Southern Ocean climatology

A new monthly climatology of Southern Ocean hydrography is constructed with updated observational dataset. CTD casts from World Ocean Database, Pangaea Database, CLIVAR and Carbon Hydrographic Data Office, Southern Ocean Database and Korean Polar Data Centre were assembled. All ‘Delayed Mode’ Argo floats profiles and ‘Real-time Mode’ or ‘Real-time Adjusted Mode’ over the within 2000 m isobath near the continental shelves are included. All flagged-good Seal-tag profiles are included. The interpolation scheme employs an elliptical detecting area to select profiles to be averaged into gridded product. The ellipse is designed to align with the dynamic height contour to consider the effect of large-scale circulation. The detecting radius confined by ellipse size varies with the bathymetry and facilitate to resolve local gradient in temperature and salinity field over the continental shelves. A timeseries is constructed by removing the temperature and salinity climatology from the individual profiles in Weddell Sea, and a clear subsurface warming is revealed. An entrainment of warm and saline anomalies from subsurface into the surface layer is captured around 2016 corresponding to the recent sea ice extent decline. A further regional analysis on the temperature and salinity anomaly signal will shed light on the heat delivery pathway and the cause of the subsurface heat entrainment.