We coupled an unstructured hydro model with an advanced column sea ice model to meet the growing demand for increased resolution and complexity in unstructured sea ice models. Additionally, we present a novel tracer transport scheme for the sea ice coupled model, and demonstrate that this scheme fulfills the requirements for conservation, accuracy, efficiency, and monotonicity in an idealized test. Our new coupled model also has good performance in realistic tests.

The homogeneous water column, named as mode water, retaining atmosphere condition and biogeochemical elements from the deep winter mixed layer, became weaker and warmer in the North Pacific subtropical Ocean in 2018–2021, even the Kuroshio Extension is stable. Locally anomalous east wind transporting warm water to the north and enhanced near-surface stratification hinder the deepening of winter mixed layer. This study has broad implications for climate change and biogeochemical cycles.

The unique observations by a Biogeochemical Argo float in the NW Pacific Ocean captured the impact of a super typhoon on upper-ocean physical and biological processes. Our result reveals typhoons can increase the surface chlorophyll through strong vertical mixing without bringing nutrients upward from the depth. The vertical redistribution of chlorophyll contributes little to enhance the primary production, which is contradictory to many former satellite-based studies related to this topic.