Alaska tidewater glacier terminus positions, 1948–2012

Abstract

A significant portion of the world's glacier ice drains through tidewater outlets, though much remains unknown about the response to recent climate change of tidewater glaciers. We present a 64 year record of length change for 50 Alaska tidewater glaciers. We use U.S. Geological Survey topographic maps to provide a base length for glaciers before 1970. Using all available cloud-free Landsat images, we manually digitize calving front outlines for each glacier between 1972 and 2012, resulting in a total of more than 10,000 outlines. Tidewater glacier lengths vary seasonally; focusing on the 36 glaciers terminating in tidewater throughout the study period, we find a mean (± standard deviation) seasonal variation of 60 ± 85 m a −1 . We use these oscillations to determine the significance of interannual changes in glacier length. All 36 glaciers underwent at least one period (≥1 year) of significant advance or retreat; 28 glaciers underwent at least one period of both significant advance and retreat. Over the entire period 1948-2012, 24 of these glaciers retreated a total (± uncertainty) of 107.95 ± 0.29 km, 11 advanced a total of 7.71 ± 0.20, and one (Chenega Glacier) did not change significantly. Retreats and advances are highly variable in time; several glaciers underwent rapid, short-term retreats of a few years duration. These retreats occurred after large changes in summer sea surface temperature anomalies; further study is needed to determine what triggered these retreats. No coherent regional behavior signal is apparent in the length record, although two subregions show a coherence similar to recent observations in Greenland.

Derivation and analysis of a complete modern-date glacier inventory for Alaska and northwest Canada

“…Arendt and others, 2006). We here distinguish land-, marine-and lake/river-terminating glaciers based on our own visual inspection of optical satellite imagery and DEMs as well as previous work (Molnia, 2008;McNabb and Hock, 2014). For this study, a glacier is classified as marine-terminating if it reaches tidewater at the time of the used image.…”

Seasonal Variations in Ice-Front Position Controlled by Frontal Ablation at Glaciar Perito Moreno, the Southern Patagonia Icefield

“…Rapid retreat and speed-up have been observed at numerous calving glaciers in Greenland (e.g., Howat et al, 2005;Amundson et al, 2008;Moon et al, 2012Moon et al, , 2015, Alaska (e.g., Meier and Post, 1987;Boyce et al, 2007;McNabb and Hock, 2014) and Patagonia (e.g., Naruse and Skvarca, 2000;Rivera et al, 2012;Sakakibara et al, 2013;Sakakibara and Sugiyama, 2014). The rapid changes take place when a glacier terminus retreats from a bedrock rise into deeper water along a reversed bed slope (e.g., Howat et al, 2005).…”

“…It provides clues to better understand the response of calving glaciers to external forcings. Studies on frontal seasonal variations have been carried out on tidewater glaciers in Greenland (Howat et al, 2010;Joughin et al, 2012;Carr et al, 2013;Schild and Hamilton, 2013;Moon et al, 2015) and Alaska (Ritchie et al, 2008;Bartholomaus et al, 2013;McNabb and Hock, 2014;Stearns et al, 2015). For example, Howat et al (2010) investigated six large marine-terminating glaciers in West Greenland with a temporal resolution of several weeks.…”

Exceptional retreat of Novaya Zemlya's marine-terminating outlet glaciers between 2000 and 2013

“…These marine-terminating outlets allow ice caps to respond rapidly to climatic change, both immediately through calving and frontal retreat (e.g. Blaszczyk et al, 2009;Carr et al, 2014;McNabb and Hock, 2014;Moon and Joughin, 2008) and also through long-term drawdown of inland ice, often referred to as "dynamic thinning" (e.g. Price et al, 2011;Pritchard et al, 2009).…”

“…During the 2000s, widespread marine-terminating glacier retreat was observed across the Arctic (e.g. Blaszczyk et al, 2009;Howat et al, 2008;McNabb and Hock, 2014;Moon and Joughin, 2008;Nuth et al, 2007), and substantial retreat occurred on Novaya Zemlya between 2000 and 2010 (Carr et al, 2014): retreat rates increased markedly from around 2000 on the Barents Sea coast and from 2003 on the Kara Sea (Carr et al, 2014). Between 1992 and 2010, retreat rates on NVZ were an order of magnitude higher on marine-terminating glaciers (−52.1 m a −1 ) than on those terminating on land (−4.8 m a −1 ) (Carr et al, 2014), which mirrors patterns observed on other Arctic ice masses (e.g.…”