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Modeling the spatial and temporal dynamics of Antarctic sea ice
Benjamin
Saenz, UC Santa Cruz, bsaenz@ucsc.edu
(Presenter)
Kevin
Arrigo, Stanford University, arrigo@stanford.edu
Sharon
Stammerjohn, University of Colorado, sharon.stammerjohn@colorado.edu
To address spatial and temporal variability in Antarctic sea ice algal production, and to establish the bounds and sensitivities of the sea ice ecosystem, a new, coupled sea ice ecosystem model was developed. In the vertical dimension, the model resolves incorporated saline brine, macronutrients concentrations, spectral shortwave radiation, and the sea ice algae community at high resolution. A novel method for thermodynamics, desalination, and fluid transfer in slushy, high-brine fraction sea ice was developed to simulate regions of high algal productivity. The processes of desalination, fluid transfer, snow-ice creation, and superimposed ice formation allowed the evolution of realistic vertical profiles of sea ice salinity and algal growth. For hemispheric simulations of Antarctic sea ice, areal sea ice concentration and motion are specified according to SSM/I passive microwave satellite estimates of these parameters.
Sensitivity testing of different snow and ice parameterizations showed that without a sub-grid scale ice thickness distribution, mean ice and snow thickness is lower and bottom sea ice algal production is elevated. Atmospheric forcing from different reanalysis data sets cause mean and regional shifts in sea ice production and associated ecology, even when sea ice extent and motion is controlled. Snow cover represents a first-order control over ice algal production by limiting the light available to bottom ice algal communities, and changes to the regional, rather than mean, snow thickness due to the use of different ice and snow representations are responsible for large differences in the magnitude and distribution of sea ice algal production. Light availability was the dominant control on sea ice algae growth over the majority of the year; however, severe nutrient limitation during late spring and summer proved to be the largest control over sea ice algal productivity. Due primarily to the more realistic approach to nutrient cycling in sea ice, we revise previous estimates of total annual sea ice algal production downward, to ~19 Tg C yr-1.
Continuing research involves examination of polar atmospheric, marine, and sea ice biophysical processes using a vertically coupled 1-D modeling approach. By determining the interplay between organic (sea ice and CESM marine ecosystem model) and inorganic (KPP mixed layer model, sea ice model, specified atmospheric properties) processes in these environments, we hope to determine the dominant modes and drivers of the polar ecosystem, and to project how marine ecosystems and carbon cycling may be altered as a result of polar climate change, particularly the phenological response to changes in ice season duration.
Presentation Type: Poster
Session: Coupled Processes at Land-Atmosphere-Ocean Interfaces
(Mon 4:00 PM)
Associated Project(s):
Poster Location ID: 76
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