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.

2010
Massom, RA, Giles AB, Fricker HA, Warner RC, Legresy B, Hyland G, Young N, Fraser AD.  2010.  Examining the interaction between multi-year landfast sea ice and the Mertz Glacier Tongue, East Antarctica: Another factor in ice sheet stability? Journal of Geophysical Research-Oceans. 115   10.1029/2009jc006083   AbstractWebsite

The Mertz Glacier tongue (MGT), East Antarctica, has a large area of multi-year fast sea ice (MYFI) attached to its eastern edge. We use various satellite data sets to study the extent, age, and thickness of the MYFI and how it interacts with the MGT. We estimate its age to be at least 25 years and its thickness to be 10-55 m; this is an order of magnitude thicker than the average regional sea-ice thickness and too thick to be formed through sea-ice growth alone. We speculate that the most plausible process for its growth after initial formation is marine (frazil) ice accretion. The satellite data provide two types of evidence for strong mechanical coupling between the two types of ice: The MYFI moves with the MGT, and persistent rifts that originate in the MGT continue to propagate for large distances into the MYFI. The area of MYFI decreased by 50% following the departure of two large tabular icebergs that acted as pinning points and protective barriers. Future MYFI extent will be affected by subsequent icebergs from the Ninnis Glacier and the imminent calving of the MGT. Fast ice is vulnerable to changing atmospheric and oceanic conditions, and its disappearance may have an influence on ice tongue/ice shelf stability. Understanding the influence of thick MYFI on floating ice tongues/ice shelves may be significant to understanding the processes that control their evolution and how these respond to climate change, and thus to predicting the future of the Antarctic Ice Sheet.

2008
Padman, L, Erofeeva SY, Fricker HA.  2008.  Improving Antarctic tide models by assimilation of ICESat laser altimetry over ice shelves. Geophysical Research Letters. 35   10.1029/2008gl035592   AbstractWebsite

Assimilation of laser altimeter data from the Ice, Cloud and land Elevation Satellite (ICESat) significantly improves the accuracy of ocean tide models for the Ross Ice Shelf (RIS). For the most energetic tidal harmonic, K(1), assimilation reduces the root-mean-square error (RMSE) between the model and a set of 16 independent tide records on and near the RIS from 6.0 to 2.8 cm, and the combined RMSE for the six most energetic tidal harmonics from 7.7 to 5.4 cm. When only the six most recent and highest-quality tide records are considered, the combined RMSE is 4.8 cm. This value is close to the uncertainty expected from tidal analyses of the short (similar to 1-2 month) validation records, indicating that assessing further improvements in tide model accuracy will require development of a higher quality validation data set. Citation: Padman, L., S. Y. Erofeeva, and H. A. Fricker (2008), Improving Antarctic tide models by assimilation of ICESat laser altimetry over ice shelves, Geophys. Res. Lett., 35, L22504, doi:10.1029/2008GL035592.