Seasonal and decadal geostrophic pathways of Pacific and Atlantic Waters
in the Arctic Amerasian Basin from observations
Abstract
We examine the geostrophic pathways of Pacific and Atlantic Waters along
isopycnal surfaces of the Arctic Ocean from Montgomery potentials using
two observation-based climatologies: the World Ocean Atlas (WOA) and the
Monthly Isopycnal & Mixed-layer Ocean Climatology (MIMOC). The decadal
mean circulation (2005-2017) shows an anticyclonic circulation for both
the summer Pacific Waters (sPW) and winter Pacific Waters (wPW, although
somewhat weaker) in the Canada Basin with subduction along the Chukchi
plateau for both water masses. On the wPW layer, the diagnostics also
highlight a year-long persistent flow from Herald Canyon on Chukchi
Shelf to the Canadian Arctic Archipelago around the Canada Basin.
Outflows are found at Nares and Fram Sraits at the density of sPW and
wPW. These outflowing waters, previously reported as Pacific Waters, are
found here to originate from the Eurasian shelf. Deeper, the Atlantic
Waters (AW) flow anticyclonically around Northwind Ridge and
cyclonically along the Alaskan shelfbreak forming a boundary current.
The subduction of warm water along the Alaskan and Chukchi shelves is
found to occur in summer on the sPW isopycnal layer, thus contributing
to transferring heat into the center of the gyre. Yet, an advection of
virtual Lagrangian particles from Pt. Barrow suggests that processes
operating on timescales shorter than a month or at interannual time
scales are the main contributors to the heat build up observed over the
past two decades. This analysis supports the hypothesis that high
frequency processes are key in shaping the subsurface heat reservoir of
the Canada Basin.