Lecture 5 - glacier and ice sheet modeling

Question 1

Favier et al (2014)

Answer 1

PIG thinning at accelerated rate (since 1980’s), currently the single largest contributor to global sea level rise in Antarctic a

• grounding line retreated by 10s km
• susceptible to MISI
• due to enhanced sub-ice-shelf melting induced by the recent alteration of circumpolar deep water circulation

non of the models produce a steady state grounding line on the reverse slope

ground pinning points increase the buttressing force and reduce imbalance

Question 2

Gladstone et al (2012)

Answer 2

PIG flow line ice sheet model coupled to a box model for cavity circulation, 5000 simulations with various inputs and parameters

uncertainties in the rate of retreat

MISI - positive feedback between GL retreat into deeper water and increased ice discharge across the GL

significant and accelerated retreat for the next two centuries

Question 3

Nick et al (2009)

Answer 3

Greenland outlet glacier dynamics
- ice acceleration, thinning and retreat begin at the calving terminus and then propagate upstream

mass loss in Greenlands outlet glaciers are transient and shouldn’t be extrapolated into future

thinning leads calving front to approach floatation and hence retreats

model doesn’t support enhanced basal lubrication as the governing process for observed changes
- even for extreme ablation doesn’t have as much effect on thinning, doesn’t trigger unstable reatreat

Question 4

Vaughan and Arthern (2007)

Answer 4

when modeling ice sheets hard to specify the stress boundary condition at the base and seaward margins interfaces

ice sheet models cannot be constantly validated and improved because of lack of data and v. long time scales

loss of buttressing effect in Antarctica