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Implications of freshwater underplating
and underwater-ice (false bottom)
in Arctic summer sea ice
School of Fisheries and Ocean Sciences
University of Alaska Fairbanks
Sookmi
Moon
Outline
™false bottom/under-ice melt pond
how they form/ temporal evolution
™IMB data
.
™Why is it important?
™Planned research work
On the under-water ice pond and false bottom
¾ Meltwater through highly permeable ice or flaws can be retained
under thin ice or in bottom depressions ՜ double diffusive convection of heat and salt at the interface
between freshwater and salt water ՜ formation of under water ice (false bottom) (Nots et al. 2003)
¾ The only process by which significant amount of new ice can be
formed during summer (Nansen 1897)
¾ H. Eicken (1994) - 8 (15%) contained stratigraphic units identified
as ice grown in under-ice ponds out Of 52 cores at 46 locations
՜ at least 5% false bottoms (avg. ice age 3 yrs)
¾ Jefferies et al. (1995) – traces of false bottom ice in 22 of 57
cores in the Beaufot Sea ՜ 10% false bottoms (avg. ice age 4 yrs)
The evolution of areal melt pond and sea ice
hydrology at the SHEBA site (Eicken et al 2002)
Stage I
Stage II
Areal pond fraction
black dot : level MY ice
diamond : deformed MY ice
The evolution of areal melt pond and sea ice
hydrology at the SHEBA site (Eicken et al 2002)
Stage III
} Stage I
Stage IV
Areal pond fraction
black dot : level MY ice
diamond : deformed MY ice
.
Under-ice ponds –reservoirs
of surface meltwater
Eicken et al (2002)
Ice growth and melt collected by IMB
2007J
.
2008D
Recording freshwater ice growth?
2012D
2011C
2012I
2012I
Why is it important?
} Low salinity of the ice affects ice strength, thermal
conductivity
stronger ice – Marine hazard
} Freshwater underplating the ice – strong osmotic stress on
organisms
} The bottom pond ice cover with low porocity acts as an
impermeable lid
Sea ice organisms – prohibited from entering and
colonizing the ice
Reintroducing anthropogenic pollutants from meltwater
(H. Eicken, 1994)
Planned research work
} Environmental factors of false bottom formation
- air/water temperature, sea ice concentration
} Model simulation (by Notz et al) and comparison
with IMB data