Abstract

--- - Coastal ocean temperatures can respond to different atmospheric and oceanic processes at local spatial scales or through remote teleconnections. This study focused on subsurface ocean temperatures (subT) at 10 m depth in Maxwell Bay, northern Antarctic Peninsula from February 2017 and January 2022. It investigated extreme warming events during austral summers and their interaction with atmospheric and oceanic conditions regionally and locally. The analysis identified active and extreme Marine Heat Waves (MHWs) in March 2017 and January-February 2020 associated with a significantly negative Southern Annular Mode index observed 3-4 months before the temperature increase. In March 2017, temperatures exceeded the climatological mean by over 1 degrees C. This anomaly was linked to a strengthened Amundsen Sea Low and a blocking anticyclone moving between the Scotia Sea and the South-West Atlantic Ocean that deflected westerly winds and facilitated the anomalous transport of warmer northern air masses to the AP. In January-February 2020, the highest recorded subT was observed (2.97 degrees C), although air-sea heat fluxes did not show a similar pattern. In February 2020, one of the most intense atmospheric heatwaves ever recorded in West Antarctica was observed. This heatwave corresponded with maximum subT and positive sea surface temperature anomalies extending throughout the western region of the Southern Ocean, related to an extremely negative Southern Annular Mode. This study provides valuable insights into the impact of strong MHWs, a phenomenon that has been less documented in Antarctic coastal regions. - Understanding how ocean temperature varies and responds to different local and remote forcings is crucial for quantifying the potential impact of temperature fluctuations on the coastal Antarctic environment. Between 2017 and 2022 in Maxwell Bay, Antarctic Peninsula, the response of subsurface ocean temperatures (subT, temperature at 10 m depth) to extreme warming events was recorded and analyzed in relation to atmospheric and oceanic conditions. Extreme warming events in the ocean, identified as Marine Heat Waves, occurred in March 2017 and in January and February 2020. In March 2017 subT exceeded the historical averaged temperature by over 1 degrees C. The increase in subT was associated with the deflection of the typically dominant westerly winds to the south, which transported warmer northern air to the Peninsula. In January 2020, the highest recorded subT was observed (2.97 degrees C). Observations suggested this warming was related to the negative Southern Annular Mode in 2019. This study provides valuable insights into the environmental variability and temperature ranges that affect Antarctic marine communities. - Subsurface ocean temperature (subT, temperature at 10 m depth) in a coastal Antarctic embayment responded to extreme warming events SubT recorded Marine Heat Waves in summers 2017 and 2020, identified as years of extreme negative Southern Annular Mode prior to extremely high subT The main dominant modes of subT variability were related to the Amundsen Sea Low and the Southern Annular Mode