A box model of circulation and melting in ice shelf caverns
- 271 Downloads
A simple box model of the circulation into and inside the ocean cavern beneath an ice shelf is used to estimate the melt rates of Antarctic glaciers and ice shelves. The model uses simplified cavern geometries and includes a coarse parameterization of the overturning circulation and vertical mixing. The melting/freezing physics at the ice shelf/ocean interface are those usually implemented in high-resolution circulation models of ice shelf caverns. The model is driven by the thermohaline inflow conditions and coupling to the heat and freshwater exchanges at the sea surface in front of the cavern. We tune the model for Pine Island Glacier and then apply it to six other major caverns. The dependence of the melting rate on thermohaline conditions at the ice shelf front is investigated for this set of caverns, including sensitivity studies, alternative parameterizations, and warming scenarios. An analytical relation between the melting rate and the inflow temperature is derived for a particular model version, showing a quadratic dependence of basal melting on small values of the temperature of the inflow, which changes to a linear dependence for larger values. The model predicts melting at all ice shelf bases in agreement with observations, ranging from below a meter per year for Ronne Ice Shelf to about 25 m/year for the Pine Island Glacier. In a warming scenario with a one-degree increase of the inflow temperature, the latter glacier responds with a 1.4-fold increase of the melting rate. Other caverns respond by more than a tenfold increase, as, e.g., Ronne Ice Shelf. The model is suitable for use as a simple fast module izn coarse large-scale ocean models.
KeywordsAntarctic ice shelves Melt rate Box model
We appreciate the very useful comments and critiques of Adrian Jenkins.
- Braun M, Humbert A, Moll A (2008) Changes of Wilkins ice shelf over the past 15 years and inferences on its stability. The Cryosphere Discuss 2:341–382Google Scholar
- Dinniman MS, Klinck JM, Smith WO (2007) Influence of sea ice cover and icebergs on circulation and water mass formation in a numerical circulation model of the Ross Sea, Antarctica. Journal of Geophysical Research–Oceans, p 112Google Scholar
- Grosfeld K, Hellmer HH, Jonas M, Sandhäger H, Schute M, Vaughan DG (1998) Marine ice beneath Filcher Ice Shelf: evidence from a multi-disciplinary approach. In: Jacobs SS, Weiss R (eds) Ocean, ice and atmosphere: interactions at Antarctic Continental margin, vol 75 of Antarctic Research Series. American Geophysical Union, Washington, DCGoogle Scholar
- Hellmer HH, Jacobs SS, Jenkins A (1998) Oceanic erosion of a floating Antarctic glacier in the Amundsen Sea. In: Jacobs SS, Weiss R (eds) Ocean, ice and atmosphere: interactions at Antarctic Continental margin, vol 75 of Antarctic research series. American Geophysical Union, Washington, DC, pp 83–100Google Scholar
- IPCC, Contribution of working group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change(2007). Climate change 2007: The physical science basis (summary for policymakers). IPCC Secretariat, GenevaGoogle Scholar
- Jacobs S, Giulivi CF (1998) Interannual ocean and sea ice variability in the Ross Sea. In: Jacobs SS, Weiss R (eds) Ocean, ice and atmosphere: Interactions at Antarctic Continental margin, vol 75 of Antarctic research series. American Geophysical Union, Washington, DCGoogle Scholar
- Jacobs SS, Hellmer HH, Doake CSM, Jenkins A, Frolich RM (1992) Melting of ice shelves and the mass balance of Antarctica. J Glaciol 38:375–387Google Scholar
- Nicholls KW, Abrahamsen EP, Buck JJH, Dodd PA, Goldblatt C, Griffiths G, Heywood KJ, Hughes NE, Kaletzky A, Lane-Serff GF, McPhail SD, Millard NW, Oliver KIC, Perrett J, Price MR, Pudsey CJ, Saw K, Stansfield K, Stott MJ, Wadhams P, Webb AT, Wilkinson JP (2006). Measurements beneath an Antarctic ice shelf using an autonomous underwater vehicle. Geophys Res Lett 33(8):L08612CrossRefGoogle Scholar
- Smedsrud LH, Jenkins A, Holland DM, Nost OA (2006) Modeling ocean processes below Fimbulisen, Antarctica. Journal of Geophysical Research–Oceans 111(C1):C01007Google Scholar
- Wong APS, Bindoff NL, Forbes A (1998) Ocean-ice shelf interaction and possible bottom water formation in Prydz Bay, Antarctica. In: Jacobs SS, Weiss, R (eds) Ocean, ice and atmosphere: interactions at Antarctic Continental Margin, vol 75 of Antarctic Research Series. American Geophysical Union, Washington, DC, pp 173–187Google Scholar