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Variability Shelf Water Temps (Cause Interannual Melt Variability (Sea…
Variability Shelf Water Temps
Amundsen Shelf Temps
Vary on interannual (~decadal) scale
(Dutrieux et al 2014)
Causes oscillation of melt rate beneath shelf
Cause Interannual Melt Variability
What controls how much warm water reaches shelf ?
Sea surface pressure difference
btwn just N & S of shelf break
Due to large scale atmos pressure pattern Δ
induced by El Nino heating & Rossby wave pattern
Changes winds at continental shelf edge
i.e. whether Westerly or Easterly on W Coast
Leading theory:
Strong Easterlies @ Shelf Break
La Nina heating oscillations over Eq Pacific
= partial cause
Cooling off West of S. America
Rossby waves carry signal to Amundsen
∴ Low pressure in Amundsen
Westerlies weakened - causing lower melt rates
Pine Ice Shelf Velocities Increased
Christianson 2016
Temperatures increased ∴
increased melt rates
thermocline raised
Ice shelf thinning ∴ buttressing removal
Result: Faster ice shelf flow
Cause: Melt increased during El Nino cycle
2009-2014
No variation grounded ice thinning rates
More persistent Δ needed --> to permeate to interior?
Signal too small to detect?
Stratification Below PIG
2009 Warm Waters
1.2°C waters beneath PIG
Induced very strong melting
2009 Thermocline lowered ~ 100m
2012 Subzero temperatures
Little melt beneath PIG
Strong Easterlies in Amundsen
Stratification varies beneath Pine Island Glacier
2009 = much
warmer vs 2012
Pine Island melting much faster
Pine Island
Shelf Model
Critical
threshold
thermocline vs seamount height
implications for melt rate
Thermocline
below seamount
little warm water reaches shelf/cavity
high seamount blocks warm water from reaching cavity
If thermocline rises sufficiently
Warm water floods cavity
(lotsa CDP water waiting to enter)
i.e. Westerlies strengthened
∴ dramatic melt rate response