On the origins and transformation of Warm Deep Water within the Weddell Gyre

The Weddell Gyre is a key region for upwelling warm deep waters, influencing ice melt and feeding newly formed bottom and intermediate waters critical for the ocean’s heat and carbon uptake. The main pathways of deep waters into the gyre are scarcely observed and poorly understood, especially in the eastern gyre. We address this gap by identifying the origin and transformation of Warm Deep Water (WDW) along the gyre pathway. Three distinct regimes are identified: Firstly, the eastern inflow is dominated by merging of Lower and Upper Circumpolar Deep Water to form WDW. The second regime occurs along the gyre’s westward-flowing southern limb, through freshening and cooling of the newly formed WDW from the surface. Lastly, lateral mixing across the northern boundary destructs WDW. Together, these findings reveal the evolution of WDW, shaped by internal and lateral mixing, highlighting the role of the Weddell Gyre in polar water mass transformation.