A mass conservation approach for mapping glacier ice thickness

M Morlighem,E Rignot,H Seroussi,E Larour,H Ben Dhia,D Aubry

doi:10.1029/2011gl048659

Abstract

The traditional method for interpolating ice thickness data from airborne radar sounding surveys onto regular grids is to employ geostatistical techniques such as kriging. While this approach provides continuous maps of ice thickness, it generates products that are not consistent with ice flow dynamics and are impractical for high resolution ice flow simulations. Here, we present a novel approach that combines sparse ice thickness data collected by airborne radar sounding profilers with high resolution swath mapping of ice velocity derived from satellite synthetic-aperture interferometry to obtain a high resolution map of ice thickness that conserves mass and minimizes the departure from observations. We apply this approach to the case of Nioghalvfjerdsfjorden (79North) Glacier, a major outlet glacier in northeast Greenland that has been relatively stable in recent decades. The results show that our mass conserving method removes the anomalies in mass flux divergence, yields interpolated data that are within about 5% of the original data, and produces thickness maps that are directly usable in high spatial-resolution, high-order ice flow models. We discuss the application of this method to the broad and detailed radar surveys of ice sheet and glacier thickness. Copyright 2011 by the American Geophysical Union.

Highlights

For example in Greenland, surface ice velocity has been measured at a high spatial resolution (30–300 m) with satellite synthetic‐aperture radar interferometry (InSAR), with low error margins; whereas ice thickness has been derived from airborne radar sounding profilers, with tracks spaced by several to tens of kilometers, collected at different epochs, and interpolated onto a regular grid using geostatistical algorithms, e.g. kriging [Deutsch and Joumel, 1997]
[4] The underlying cause of these deviations in flux divergence is that the ice thickness data are used beyond their actual spatial resolution and their geostatistical interpolation onto a finer grid violates the conservation of mass
[5] Here, we propose a new approach, based on mass conservation, to infer ice thickness onto a high spatial‐resolution mesh by combining sparse ice thickness data from radar sounding profilers with dense, high spatial‐resolution ice velocity data collected by swath mapping satellites and ancillary data

Summary

Introduction

[2] Important ice sheet characteristics such as ice thickness, surface elevation or surface velocity are most efficiently derived from airborne and satellite platforms carrying instruments operating at different spatial resolutions and deployed at different epochs. For example in Greenland, surface ice velocity has been measured at a high spatial resolution (30–300 m) with satellite synthetic‐aperture radar interferometry (InSAR), with low error margins (a few m/yr); whereas ice thickness has been derived from airborne radar sounding profilers, with tracks spaced by several to tens of kilometers, collected at different epochs, and interpolated onto a regular grid using geostatistical algorithms, e.g. kriging [Deutsch and Joumel, 1997]. [4] The underlying cause of these deviations in flux divergence is that the ice thickness data are used beyond their actual spatial resolution and their geostatistical interpolation onto a finer grid violates the conservation of mass. Farinotti et al [2009] employed a method, derived from the same principle, to determine the ice volume of Swiss alpine glaciers All these studies, suffer from significant deviations from the original thickness data, i.e., by hundreds. After introducing the method and the optimization process, we discuss its application to a major Greenland outlet glacier, describe the results and conclude on the applicability of this approach to the broad, detailed surveys of glaciers and ice sheets

Method

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Results

Discussion

Findings

Conclusions