Abstract
We examine the effects of the submesoscale in mediating the response to
projected warming of phytoplankton new production and export using
idealized biogeochemical tracers in a high-resolution regional model of
the Porcupine Abyssal Plain region of the North Atlantic. We quantify
submesoscale effects by comparing our control run to an integration in
which submesoscale motions have been suppressed using increased
viscosity. The warming climate over the 21st century reduces resolved
submesoscale activity by a factor of 2-3. Annual new production is
slightly reduced by submesoscale motions in a climate representative of
the early 21st-century and slightly increased by submesoscale motions in
a climate representative of the late 21st-century. Resolving the
submesoscale, however, does not strongly impact the projected reduction
in annual production under representative warming. Organic carbon export
from the surface ocean includes both direct sinking of detritus (the
biological gravitational pump) and advective transport mediated
pathways; the sinking component is larger than advectively mediated
transport by up to an order of magnitude across a wide range of imposed
sinking rates. Submesoscales are responsible for most of the advective
carbon export, however, which is thus largely reduced by a warming
climate. In summary, our results demonstrate that resolving more of the
submesoscale has a modest effect on present-day new production, a small
effect on simulated reductions in new production under global warming,
and a large effect on advectively-mediated export fluxes.