Abstract. Ocean acidification driven by the uptake of anthropogenic CO2 by the
surface oceans constitutes a potential threat to the health of marine
ecosystems around the globe. The Arctic Ocean is particularly vulnerable to
acidification and thus is an ideal region to study the progression and
effects of acidification before they become globally widespread. The
appearance of undersaturated surface waters with respect to the carbonate
mineral aragonite (ΩA<1), an important threshold
beyond which the calcification and growth of some marine organisms might be
hindered, has recently been documented in the Canada Basin and adjacent
Canadian Arctic Archipelago (CAA), a dynamic region with an inherently strong
variability in biogeochemical processes. Nonetheless, few of these
observations were made in the last 5 years and the spatial coverage in
the latter region is poor. We use a dataset of carbonate system parameters
measured in the CAA and its adjacent basins
(Canada Basin and Baffin Bay) from 2003 to 2016 to describe the recent state
of these parameters across the Canadian Arctic and investigate the amplitude
and sources of the system's variability over more than a decade. Our
findings reveal that, in the summers of 2014 to 2016, the ocean surface
across our study area served as a net CO2 sink and was partly
undersaturated with respect to aragonite in the Canada Basin and the Queen
Maud Gulf, the latter region exhibiting undersaturation over its entire
water column at some locations. We estimate, using measurements made
across several years, that approximately a third of the interannual
variability in surface dissolved inorganic carbon (DIC) concentrations in the CAA results from fluctuations in
biological activity. In consideration of the system's variability resulting
from these fluctuations, we derive times of emergence of the anthropogenic
ocean acidification signal for carbonate system parameters in the study
area.