File formerly called: MOSAiC_ocean_workingroup.doc
----------------Ocean Breakout Group:
Processes driving changes in the hydrologic cycle
1. What is driving ice melt? Competition between more melt, accelerated hydrology, stronger
stratification, more heat storage. Chain of events leads to the phenomenon of Minimum in
sea ice cover, which is followed by a “recovery” year. Melt more ice leads to more fresh water,
which in turn leads to more ice formation in the recovery year. There is a major knowledge
gap in the annual cycle owing to sparse data coverage from autumn into winter and winter
into spring. Understanding the relative contribution of Pacific Summer Water and Atlantic
Water to sea ice melt are factors in determining the heat budget leading to melt.
2. Freeze up and melt out processes in autumn and spring. Asymmetry between locations of
melt and freeze. Leads to depositions of freshwater in certain regions (stratification). Heat
release from NSTM and other heat sources in the ocean. Possibly need several platforms to
evaluate radiation budget in different regions.
3. Interannual variability in Arctic Freshwater budget. (probably not for MOSAiC)
4. Freshwater export: Seasonal and Interannual. (probably not for MOSAiC)
5.
Boundary layer at the heterogeneous air-ice-ocean interface
1. What are the processes that dominate the evolution of the mixed layer and how does it vary
with changing ice cover through the seasons and across the basin?
2. Atmospheric Boundary layer is heavily influenced by energy inputs from ocean.
Heterogeneity between ice cover and open water lead to large deviations in the boundary
layer (e.g. stability, convection, large deviations, roughness length, sensible and latent heat
fluxes.
3. Canonical models (MOST) are possibly adequate but need better constraint on the
parameters.
4. Exchange of aerosols depend on factors unique to sea ice, including degradation of ice-derived
marine organics
5. Net transport of trace gases is intimately coupled to ice-ocean boundary layer turbulence. Sea
ice both stimulates and mitigates boundary layer turbulence and thus air-sea gas exchange.
6.
Processes governing isopycnal and diapycnal transport of heat and freshwater
7. The role of diapycnal mixing in the Arctic. Known to be historically weak. Likely to change
with changes in ice cover.
8. Role of meso and submesoscale lateral mixing in affecting interior stratification. Heat and
freshwater entering the Arctic and leading to the basin scale circulation. For example, vertical
exchanges at sharp ocean fronts, driven by strong atmospheric forcing. Or sharp lateral
gradients in atmospheric forcing on the upper ocean.
9. What processes drive exchange between the shelf and the ocean basin? Boundary currents,
coastal currents, mesoscale eddies, topographic steering and marginal ice zone processes,
upwelling. Heat and freshwater entering the Arctic and leading to the basin scale circulation.
10. Brine rejection and its role in determining the mixed layer properties, including thickness,
heat exchange with atmosphere, biogenic gas transport, salt fluxes and nutrient renewal.
11. Polynyas and convection. Is ice formation leading to changes in interior water formation
(accelerated hydrological cycle)? (probably not for MOSAiC).
Arctic energy budget in a warming climate
1. New energy source for melting sea ice:
a. Accumulation of heat in the ocean (and warming atmosphere).
b. Delays freeze up, energy is persistent through winter.
c. “Pacific summer” or warm shelf water is subducted into central basin, trapped
between seasonal and permanent pycnocline.
2. Ice-albedo-ocean effect: Reduce ice cover, increase absorption, leads to ocean heat storage
beneath mixed layer.
3. Insolation
4. Oceanic heat convergence: Ocean dynamics, circulation. Focus on upper ocean (0-200 m).
Halocline matters because this is the region that “might” affect the sea ice in the long run.
5. Vertical exchanges from ocean heat convergence lead to enhanced primary productivity and
food web concentration along shelf breaks, up to higher trophic levels (e.g. krill and wales).
Understanding ecosystem response to changes in sea ice
1. How do species successions and distributions change with shorter sea ice season?
2. Feedbacks between sea ice melt and krill migration and grazing.
3. Impact of mixing processes – both lateral and vertical on ecosystem response and on the
upper ocean carbon cycle.
4. What are the interactions between physical settings and biological hotspots, such as frontal
structures, the marginal ice zone, submarine bathymetry, flow convergences?
Physical-biogeochemical coupling
1. Feedbacks between ocean color (phytoplankton, CDOM, DOC) and the absorption of solar
ration by the upper ocean. This is a biological feedback on ocean thermohaline structure.
2. Ice edge associated upwelling, from surface divergence. How does this lead to e.g. nutrient
transport, changes in mixed layer properties?
3. Does sea ice make significant contributions to the ocean solubility pump? E.g. through CaCO3
trapping, through regulating the annual cycle of air-sea gas exchange.
4. What are the dependencies between open water primary production and sea ice? E.g. through
the deposition of iron micronutrients, stratification, etc.?
5. What is the net annual production/consumption of CO2, O2, DMS and methane in sea ice?
6. What is the net annual production/consumption of CO2, O2, DMS and methane in the water
column beneath sea ice?
7. Can we test the seeding hypothesis during MOSAiC?
8. Coupling between increased primary productivity and increased aerosol production.
9. What role does brine rejection play in transporting alkalinity and inorganic carbon out of the
mixed layer? What is the strength of this transport in a polynya? In the central sea ice zone?
10. Ice thickness changes – we lack knowledge on what induces the ice melting process. Ocean
heat (sw radiation) through penetration in leads. Need more distributed equipment to
measure more detailed structure of open ocean.