  This paper presents the first estimate of the seasonal cycle of ocean and sea
ice net heat and freshwater (FW) fluxes around the boundary of the Arctic
Ocean. The ocean transports are estimated primarily using 138 moored
instruments deployed in September 2005 to August 2006 across the four main
Arctic gateways: Davis, Fram and Bering Straits, and the Barents Sea Opening
(BSO). Sea ice transports are estimated from a sea ice assimilation product.
Monthly velocity fields are calculated with a box inverse model that enforces
volume and salinity conservation. The resulting net ocean and sea ice heat and
FW fluxes (annual mean $\pm$ 1 standard deviation) are 175 $\pm$48 TW and 204
$\pm$85 mSv (respectively; 1 Sv = 10$^{6} m^{3} s^{-1}$). These boundary fluxes
accurately represent the annual means of the relevant surface fluxes. Oceanic
net heat transport variability is driven by temperature variability in upper
part of the water column and by volume transport variability in the Atlantic
Water layer. Oceanic net FW transport variability is dominated by Bering Strait
velocity variability. The net water mass transformation in the Arctic entails a
freshening and cooling of inflowing waters by 0.62$\pm$0.23 in salinity and
3.74$\pm$0.76C in temperature, respectively, and a reduction in density by
0.23$\pm$0.20 kg m$^{-3}$. The volume transport into the Arctic of waters
associated with this water mass transformation is 11.3$\pm$1.2 Sv, and the
export is -11.4$\pm$1.1 Sv. The boundary heat and FW fluxes provide a benchmark
data set for the validation of numerical models and atmospheric re-analyses
products.
