MONITORING GLACIER CHANGE USING GOOGLE EARTH

Monitoring the retreat of ice margins and changes in glacier area is a critically important element of evaluating the effects of climate change in mountainous areas. Google Earth™ provides a convenient way to rapidly examine changes over several decades, using the History, Polygon, and Path functions. We use these tools to compute changes in three well studied areas—outlet glaciers of Vatnajökull in Iceland; outlet glaciers of the Columbia Ice Cap in the Canadian Rocky Mountains; and several glaciers in the Southern Alps of New Zealand. Two of the larger Iceland glaciers, which terminate in proglacial lakes, have lost more than 25 km² of area in the terminus from 1985 to 2018 or 2020, with terminus retreat rates of 75-150 m/yr, whereas other glaciers that terminate on land have lost less than 5 km² over that same time, and several have been fluctuating in the last two decades. Our interpretation of imagery from 1985 and 2022 shows that the Athabasca glacier in Canada has lost 0.67 km² of area, and the front has retreated 0.48 km (~13m/yr). The Columbia glacier on the west side of the ice cap has lost 0.42 km² but retreated 0.62 km (more than 16 m/yr). Our analysis of the Tasman glacier in New Zealand yields a terminus retreat rate of more than 130 m/yr between 1985 and 2019 due to calving into the proglacial Lake Tasman. The Dall glacier, which does not terminate in a lake, has retreated around 80 m/yr over a similar period. These examples illustrate the variety of different measurements that be extracted from Google Earth™, providing an easy means of assessing glacier change, at least over the last few decades. The main limitations in studying glacier change through time in this manner are inconsistent georectification among different images, lower resolution of early images, limitation to 2D analysis, and consistency in our own measurements.