Oral

IAPSO

JPC06 - Understanding and predicting the Arctic Ocean and Sea Ice states: Insights, Challenges, and Future Directions.

Revisiting the Hydrographic Changes in the Upper Ocean of a Relaxing Beaufort Gyre During 2013-2019

The stability of the upper ocean is crucial for the exchange of momentum, heat, and salt between sea ice and subsurface warm water in the Beaufort Gyre (BG) region of the Arctic Ocean. Here, based on multiple in-situ observations, the shifting phases of the BG during 2003-2023 are objectively defined. We find that the potential energy anomaly (PEA) in the upper 55 m decreased from 130.9��2.3 J/m3 during 2006-2012 with BG intensification to 90.3��2.0 J/m3 during 2013-2019 with BG relaxation. Further, the mixed layer became saltier and deeper across all seasons. Decreasing PEA indicates an overall weaker stratification in the upper water column which promotes stronger vertical entrainment. We also find that the mixed layer heat content increased across nearly all seasons, except during July to September (summer). Our analysis using a Price?Weller?Pinkel model suggests that the cause of this warming was not atmospheric heat fluxes from above, but rather subsurface heat entrainment upward. The key mechanism is the seasonal amplitude of PEA is smaller during 2013-2019 when the BG relaxes, thereby the upper BG can mix to greater depths under the same surface salt flux. This is important for the future evolution of the sea ice melting and oceanic vertical mixing when the BG relaxes.