Image courtesy of LLNL
Mean seasonal fields of sea ice concentration (%) in (a) (left) winter (DJF) from SSM/I data and (right) POP-CICE; and in (b) (left) summer (JJA) from SSM/I data and (right) POP-CICE from Ivanova, D. P., J. L. McClean, and E. C. Hunke (2012), Interaction of ocean temperature advection, surface heat fluxes and sea ice in the marginal ice zone during the North Atlantic Oscillation in the 1990s: A modeling study, J. Geophys. Res., 117,C02031, doi:10.1029/2011JC007532.
The polar ice edge, or marginal ice zone (MIZ), is a key area since it is erodes first; however, it is not known how much of the erosion results from atmospheric heating or from oceanic advection of warm waters. This DOE-funded model study uses the DOE supported POP ocean and CICE sea-ice models to investigate and compare these processes.
The researchers found that bottom ice melt dominates the top ice melt, signifying the role of the ice-ocean heat exchange for the ice thermodynamics.
The model passes an important test of sea-ice distribution changes: when the model is driven by the observed-reanalysis winds of the 1990’s, it successfully simulates the observed dipole pattern of ice concentration changes characteristic of the changes associated with North Atlantic Oscillation pressure and circulation changes. The model successfully simulates the first mode of sea ice concentration variability, which is characterized by a dipole pattern of ice concentration anomalies, coherent with the atmospheric North Atlantic Oscillation (NAO) pressure pattern. The model ocean-ice system was forced with NCEP/NCAR atmospheric reanalysis and then run for the two NAO periods during the 1990s. The upper ocean mixed layer heat budgets were analyzed in the Barents, Nordic, and Irminger Seas to determine the winter-to-winter changes in the ocean heat advection and mixed layer net fluxes and these were then related to the ice changes. The ocean advection anomalies were also closely related to anomalous bottom ice melt rates. However although the oceanic temperature advection is of the same order of magnitude as the net atmospheric heat fluxes, the latter are always larger. Entrainment of heat from the deeper ocean may also play a key role in the upper ocean heat balance and this may be strongly influenced by ocean heat advection. Future research will consider the role of the deeper ocean upwelling, and will continue to investigate the relative importance of atmospheric and oceanic processes in eroding polar sea-ice.
Lawrence Livermore National Laboratory
DOE Office of Science Biological and Environmental Research (BER) program
Ivanova, D. P., J. L. McClean, and E. C. Hunke. “Interaction of ocean temperature advection, surface heat fluxes and sea ice in the marginal ice zone during the North Atlantic Oscillation in the 1990s: A modeling study,” J. Geophys. Res. 117 C02031 (2012). [DOI: 10.1029/2011JC007532].
University, DOE Laboratory