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Fresh water balance of the Arctic Ocean

A. Jahn, R. Gerdes, A. Nguyen, Ye. Aksenov, W. Maslowski, C. Herbaut

This research will attempt to answer the fundamental questions: How does fresh water enter the Arctic Ocean system? How does it move about including undergoing phase changes? How does it finally exit the system?  First, groups responsible for this activity will evaluate how well models can reproduce pan-Arctic freshwater budget by comparison of model outputs budgets of Serreze et al. (2006). We anticipate that most (but perhaps not all) models will achieve freshwater balance in the upper layers including the AW after several decades. How these balances are actually achieved will provide insight into model physics.  Zhang and Steele (2007) have shown how the magnitude of numerical vertical mixing can affect salinity structure within the Beaufort Gyre. More information about these experiments is available below.

FW export variability

a.    Questions :

  • What is forcing FW export variability? Role of atmospheric forcing? Is NAO/AO suitable for comparison with FW export variability?
  • What controls changes in the phase shift between the Fram Strait and CAA FW export?
  • What is the mean model FW export through CAA and Fram Strait?

b.    Experiments :

  • Assess variability of FW exports in different models, and determine which role atmospheric forcing and SSH fields play in forcing this variability in different models and in the model mean
  • Investigate how and why the phase of the FW export through Fram Strait and the CAA changes, and how this might depend on the CAA resolution in models
  • Compute model mean FW exports, and compare with observational budget of Serreze et al. 2006.

c.    Which fields :

  • Simulation from 1948-2008, or if not possible shorter recent sub periods
  • Monthly mean liquid and solid FW flux (relative to 34.8, over full depth of Strait, negative FW allowed) through CAA, Fram Strait (~79°N), Barents Sea (Svalbard to Norway, i.e. along 20 degree E?), and Bering Strait for 1948 – 2008.
    • Fluxes should be calculated over full depth of straits, relative to 34.8, negative FW allowed (i.e., include all salinities, not just salinities under 34.8)
    • Need information how fluxes were calculated (with monthly means, daily, instantaneous values?)
    • Need total fluxes, as well as the fluxes in and out of Arctic Ocean
    • In high resolution models, needs fluxes for individual straits in CAA: Nares Strait, Jones Sound, Lancaster Sound, Davis Strait and Hudson Strait.
  • Monthly mean fields of river runoff and net precipitation FW fluxes
  • Need information on whether restoring is used, and details on restoring procedure
  • Need details on how river runoff is added (virtual salt flux? If yes, which reference density is used?), sea ice density, sea ice salinity, snow density
  • Need information on model resolution and grids (bi-polar, tri-polar, etc.) and forcing (NCEP, ERA-40, etc?)
  • Monthly SLP (from the forcing used) and SSH fields

Solid and liquid FW export and diversion of liquid FW north of Fram Strait and impact of this on sea ice

a.   Questions:

  • How does a phase change in the export of FW affect sea-ice in the Arctic through recirculation?
  • What vertical model resolution is required to realistically track liquid FW from summer melt?
  • How is liquid FW partitioned between wind-driven boundary layer transport and ocean geostrophic flow?
  • How much FW is Ekman pumped to levels below the IOBL direct stress-driven transport?

b.   Experiments:

  • Impact of model vertical resolution on IOBL FWT
  • Impact of early season melting (e.g., high IAF in June) on distribution of ice and liquid FW.
  • Impact of Ekman pumping on liquid FWT

c.   Which fields:

  • Liquid FW transport: FWT=Integral[v*{(34.8-S)/34.8}]dz
  • Ice FW transport
  • Ice/ocean interface fluxes