A Lagrangian view of Pacific water inflow pathways in the Arctic Ocean during model spin-up

In this study, we identify the routes of Pacific water within the Arctic Ocean using velocity fields, derived from the spin-up of a numerical model, and representing different circulation states within the basin. Lagrangian analysis shows there are two major routes of Pacific inflow water circulating in the Arctic Ocean, a Transpolar route and an Alaskan route. Those two routes transport more than 70% of the Pacific water, ∼50% of which flows through the central Canadian Arctic Archipelago (CAA), to the Atlantic. The outer edge (close to the coast) of Pacific inflow water routes, especially within the interior basin, is close to the 7 m isopleth of the upper (above 227 m) freshwater content. The proportion of Pacific water flowing along the two routes significantly changes with the spatial distribution of freshwater within the Canadian Basin. When more freshwater occupies the Beaufort Gyre (during the 5th year of spin-up), almost all the Pacific water entering the central CAA is from the Transpolar route. However, with a much weaker (flattened) Beaufort Gyre due to the loss of a significant amount of freshwater, ∼65% of the Pacific water entering the central CAA is from the Alaskan route, resulting in younger Pacific water reaching the central CAA. Thus, we propose that not only the amount of freshwater but also its spatial distribution within the Canadian Basin play an important role in the Arctic Ocean circulation system, although the total volume transport (∼0.35 Sv, 1 Sv = 10 6 m 3 s - 1 ) of Pacific water through the central CAA shows little variation with time.