Assessing the Atlantic Water Pathways To The Arctic In a High-Resolution NEMO Model

Most Atlantic Water (AW) enters the Arctic Ocean through the West Spitzbergen Current, passing north of Svalbard, either moving along the upper slope or passing over and around the Yermak Plateau. Recent model studies (Koenig et al. 2017 and Crews et al. 2019) have improved our understanding of these pathways but were limited to periods of 1-5 years. This is insufficient for examining the contributions of AW inflow to climate-scale problems such as the ‘Atlantification’ of the Arctic.

In this study we use 23 years (1995-2018) of high resolution (~1/24°) velocity fields from a NEMO 3.6 model (DOI: 10.5281/zenodo.2682406) allowing us to examine the geographic distributions and strengths of AW inflow pathways using a Lagrangian particle tracking approach. Virtual particles were released on a section at 30° E and tracked backwards in time using the PARCELS 2.0 particle tracking system (Delandmeter and van Sebille 2019).

For the present analysis, we focus on trajectories of particles which are contained in AW layer at the release line (SA>34.9 and CT>2°C) and could be tracked backwards to the Nowegian Sea (here taken as south of 75° N). A control line was selected across the Yermak Plateau to allow us to separate particles passing through the Svalbard and Yermak branches. Using these particle trajectories, we created a time-series of transport of AW reaching the southern rim of the western Nansen Basin. The transport was found to vary between 0.5 Sv and 3.75 Sv, comparable to previous studies (e.g. Beszczynska-Möller et al. 2012), and to be dominated, on average, by the Yermak Branch.