Publications

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2018
Padman, L, Siegfried MR, Fricker HA.  2018.  Ocean tide influences on the Antarctic and Greenland ice sheets. Reviews of Geophysics. 56:142-184.   10.1002/2016rg000546   AbstractWebsite

Ocean tides are the main source of high-frequency variability in the vertical and horizontal motion of ice sheets near their marine margins. Floating ice shelves, which occupy about three quarters of the perimeter of Antarctica and the termini of four outlet glaciers in northern Greenland, rise and fall in synchrony with the ocean tide. Lateral motion of floating and grounded portions of ice sheets near their marine margins can also include a tidal component. These tide-induced signals provide insight into the processes by which the oceans can affect ice sheet mass balance and dynamics. In this review, we summarize in situ and satellite-based measurements of the tidal response of ice shelves and grounded ice, and spatial variability of ocean tide heights and currents around the ice sheets. We review sensitivity of tide heights and currents as ocean geometry responds to variations in sea level, ice shelf thickness, and ice sheet mass and extent. We then describe coupled ice-ocean models and analytical glacier models that quantify the effect of ocean tides on lower-frequency ice sheet mass loss and motion. We suggest new observations and model developments to improve the representation of tides in coupled models that are used to predict future ice sheet mass loss and the associated contribution to sea level change. The most critical need is for new data to improve maps of bathymetry, ice shelf draft, spatial variability of the drag coefficient at the ice-ocean interface, and higher-resolution models with improved representation of tidal energy sinks.

2012
Mueller, RD, Padman L, Dinniman MS, Erofeeva SY, Fricker HA, King MA.  2012.  Impact of tide-topography interactions on basal melting of Larsen C Ice Shelf, Antarctica. Journal of Geophysical Research-Oceans. 117   10.1029/2011jc007263   AbstractWebsite

Basal melting of ice shelves around Antarctica contributes to formation of Antarctic Bottom Water and can affect global sea level by altering the offshore flow of grounded ice streams and glaciers. Tides influence ice shelf basal melt rate (w(b)) by contributing to ocean mixing and mean circulation as well as thermohaline exchanges with the ice shelf. We use a three-dimensional ocean model, thermodynamically coupled to a nonevolving ice shelf, to investigate the relationship between topography, tides, and w(b) for Larsen C Ice Shelf (LCIS) in the northwestern Weddell Sea, Antarctica. Using our best estimates of ice shelf thickness and seabed topography, we find that the largest modeled LCIS melt rates occur in the northeast, where our model predicts strong diurnal tidal currents (similar to 0.4 m s(-1)). This distribution is significantly different from models with no tidal forcing, which predict largest melt rates along the deep grounding lines. We compare several model runs to explore melt rate sensitivity to geometry, initial ocean potential temperature (theta(0)), thermodynamic parameterizations of heat and freshwater ice-ocean exchange, and tidal forcing. The resulting range of LCIS-averaged w(b) is similar to 0.11-0.44 m a(-1). The spatial distribution of w(b) is very sensitive to model geometry and thermodynamic parameterization while the overall magnitude of w(b) is influenced by theta(0). These sensitivities in w(b) predictions reinforce a need for high-resolution maps of ice draft and sub-ice-shelf seabed topography together with ocean temperature measurements at the ice shelf front to improve representation of ice shelves in coupled climate system models.