Causal Links Among Sources of Heat in the Arctic Surface Mixed Layer and Seasonal Sea Ice Melt

In recent decades, the ocean's influence on Arctic sea ice has become increasingly pronounced. The surface mixed layer (SML) serves as a critical interface between the underlying ocean and sea ice, mediating heat transfer between them. However, the links between the SML and seasonal sea ice changes, as well as the dominant mechanisms governing this interaction, remain insufficiently understood. This study uses in situ sea‐ice drift data and the Liang–Kleeman information flow to quantify the causal relationship between the SML and sea ice thickness on the Eurasian Basin side, revealing a clear two‐way cause‐effect relationship. Furthermore, the links between seven heat sources in the SML and seasonal sea‐ice melt are also quantified. Vertical turbulence emerges as the primary contributor to heat transfer in the SML near Fram Strait and north of Svalbard, where the halocline is weak and Atlantic Water (AW) remains relatively warm. When the SML heat content is high, horizontal advection dominates, while vertical advection becomes more important only when AW is ventilated upward. In contrast, in the Nansen and Amundsen basins, where the influence of AW heat is weaker, the relationship between the SML and seasonal sea‐ice melt is primarily driven by sea‐ice melting, with the SML itself being influenced mainly by vertical turbulence and ice‐ocean heat forcing.