Atlantic Water Boundary Current Along the Southern Yermak Plateau, Arctic Ocean

The major ocean current that carries heat into the Arctic Ocean splits into three main branches of Atlantic Water (AW) and recirculations when it encounters the Yermak Plateau (YP) located north of Svalbard. While the branches that cross the plateau and recirculations have been extensively studied, there has been limited observation of the transport and variability of the Yermak branch. In this study, we present year-round observations from an array of three moorings that were deployed across the boundary current on the southern slope of the YP. The temporal-averaged sections show a surface-intensified AW core, which is strongest in winter but also persistent throughout the record within the upper 500 m. The volume transport of AW is highest in fall (1.4 +/- 0.2 Sv; 1 Sv = 10(6) m(3) s(-1)) and decreases to 0.8 +/- 0.1 Sv in summer. Beneath a surface-intensified core, the velocity profile has a minimum at middepth, gradually increasing toward the bottom. This cold, bottom-intensified current is detectable in all seasons and reaches a maximum transport of 1.5 Sv in spring. The transport of AW is regulated by wind stress curl and coastal upwelling along the northwestern shelf of Svalbard. A positive wind stress curl increases the volume transport in the Yermak branch, thereby reducing the Svalbard branch transport. Eddy kinetic energy is surface-intensified and decreases to negligible values below 500 m. In the upper 500 m, the average baroclinic conversion in winter and summer is about 1 x 10(-5) W m(-3), which is 4-10 times the barotropic conversion rates. Plain Language Summary We conducted year-long measurements of temperature, salinity, and ocean currents using an array of instruments in the southern part of Yermak Plateau, located northwest of Svalbard. The array covers the ocean current that carries warm Atlantic Water-an important contributor of heat to the Arctic Ocean. Using the observations, we describe the structure and seasonal changes of the currents and how much water they transport into the Arctic. This is the first study to collect year-round data on this part of the ocean. We found that the amount of warm water transported varied by season and was highest in the fall. Wind patterns also influenced how the warm water flow was divided between different pathways. We also discovered a previously unknown deep current of cold water flowing in the same direction as the warm water current. This cold water flow was persistent in all seasons and transported similar amounts of water as the warm water flow.