Antarctic tidal melting ... first results

Question:

Tides modulate ice shelf basal melting
hence potentially impact Antarctic basal mass balance
HOWEVER, total contribution to mass loss unknown

Approach:

Circum-Antarctic ocean-ice shelf model
that reproduces observed tides and basal melting
Experiment tides on/off

Model Evaluation: Tides

sigma_comb = measure for model bias in tidal energy
sigma_comb of other models: 7 - 23 cm

Complex RMSD to ATG:

Sigma_comb = 15 cm

M2: 12 cm

N2: 3 cm

K1: 7 cm

O1: 5 cm

Model Evaluation: Tides

good overall accuracy
biggest differences at grounding zone of large ice shelves
possibly due to tidal flexure and unknown bathymetry

Our total basal mass loss: 1248 Gt/a

1735 ± 164 Gt/a

Rignot et al. 2013

Evaluation: basal melting

total mass loss agrees well with observations
circum-Antarctic pattern ok
regional patter: little refreezing and strong melting at ice front

Satellite based studies:

1090 - 1600 Gt/a

Results: tidal melting

tidal melting contributes
140 Gt/yr (14%) of total basal mass loss
change in regional melting/refreezing up to more than 100%
cold water ice shelves more impacted than warm ones

Summary

tides contribute 140Gt/yr (14%) to Antarctic basal mass loss
tides modulate local melt rates of cold ice shelves by up to 100%
highlights the need to account for tides when modeling Antarctic basal mass balance

Thanks !

Results: nodal tidal melting

integrated effect small
local impact maybe relevant around important grounding zones

Tidal amplitudes are modulated in 18.6 year cycle
Antarctic tides:
- weakest in 2015
- strongest in 2024
Experiment: 2015 tides vs. 2024 tides

Upcoming: in-band variance and mean melting

Upcoming: 1 km resolution

St-Laurent, P., J. M. Klinck, and M. S. Dinniman (2015), Impact of local winter cooling on the melt of Pine Island Glacier, Antarctica, J. Geophys. Res. Oceans, 120