Marine Cold Air Outbreaks (MCAOs) have a profound influence on
atmospheric conditions and the surface-atmosphere heat exchange in Fram
Strait and Svalbard. Comparing the global reanalysis ERA5 to its novel
Arctic counterpart CARRA for November-March 1991-2020, we investigate
the surface turbulent heat fluxes and the spatial characteristics of
MCAOs throughout the troposphere. We find that the sensible heat flux
from the surface to the atmosphere is substantially higher in CARRA,
while the latent heat flux is higher in ERA5. For sensible heat flux,
the differences scale with the magnitude, leading to maximum
disagreement over the ice-free ocean where the flux is high. Accounting
for the varying magnitude over different surface types, we find the
largest relative disagreement over sea ice. During MCAOs, negative
anomalies in temperature and specific humidity are present throughout
the entire troposphere in both reanalyses. Meanwhile, positive heat flux
anomalies are found in northwestern Fram Strait, where the sensible heat
flux from the ocean to the atmosphere is roughly doubled during MCAOs.
Around much of Svalbard, sea ice decline has caused positive trends in
the surface-atmosphere potential temperature difference forming the
basis of the MCAO index, leading to higher heat fluxes. In Fram Strait
however, both reanalyses show negative trends in the MCAO index and the
heat fluxes in January, when the increase in potential temperature is
larger at 850 hPa than at the surface.