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<p>In 2012, a persistent marine heatwave (MHW) along the U.S. Mid-Atlantic coastline developed, driving the majority of the observed ~ 4&#xa0;°C warming in the Gulf Stream region since 1982. In this study, the warm SST trend accentuated by this MHW observed in high-resolution satellite measurements is used to force a global atmospheric general circulation model. Through simulation of the atmospheric response and a subsequent series of simple ocean model diagnostics to understand the air-sea interactions, a negative feedback mechanism is revealed whereby cyclonic surface winds over the warm anomaly generate cyclonic wind stress, Ekman suction, and a change in the geostrophic currents. The calculations imply a cooling tendency over the warming region through horizontal temperature advection driven by a sea level gradient, which becomes dominant after 2&#xa0;years. The role of evaporative heat loss is also accounted for and is found to be unimportant after approximately 2&#xa0;years (when the advection-driven feedback attains a significantly larger magnitude). These results lead to new insight into the dynamics that couple the ocean and atmosphere in the presence of long-term warm SST trends, specifically by weighing factors driving both the dissipation and persistence of MHW events in the midlatitudes.</p>

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Air-sea interactions over persistent warm midlatitude SST anomalies

  • 期刊论文

  • 发表日期：

    2025年7月11日

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  • Sydney M. Kramer,
  • Kristopher B. Karnauskas

摘要

In 2012, a persistent marine heatwave (MHW) along the U.S. Mid-Atlantic coastline developed, driving the majority of the observed ~ 4 °C warming in the Gulf Stream region since 1982. In this study, the warm SST trend accentuated by this MHW observed in high-resolution satellite measurements is used to force a global atmospheric general circulation model. Through simulation of the atmospheric response and a subsequent series of simple ocean model diagnostics to understand the air-sea interactions, a negative feedback mechanism is revealed whereby cyclonic surface winds over the warm anomaly generate cyclonic wind stress, Ekman suction, and a change in the geostrophic currents. The calculations imply a cooling tendency over the warming region through horizontal temperature advection driven by a sea level gradient, which becomes dominant after 2 years. The role of evaporative heat loss is also accounted for and is found to be unimportant after approximately 2 years (when the advection-driven feedback attains a significantly larger magnitude). These results lead to new insight into the dynamics that couple the ocean and atmosphere in the presence of long-term warm SST trends, specifically by weighing factors driving both the dissipation and persistence of MHW events in the midlatitudes.