Dynamic changes in outlet glaciers in northern Greenland from 1948 to 2015

Abstract

The Greenland Ice Sheet (GrIS) is losing mass in response to recent climatic and oceanic warming. Since the mid-1990s, marine-terminating outlet glaciers across the GrIS have retreated, accelerated and thinned, but recent changes in northern 10Greenland have been comparatively understudied. Consequently, the dynamic response (i.e. changes in surface elevation and velocity) of these outlet glaciers to changes at their termini, particularly calving from floating ice tongues, remains unknown.Here we use satellite imagery and historical maps to produce an unprecedented 68-year record of terminus change across 18 major outlet glaciers and combine this with previously published surface elevation and velocity datasets. Overall, recent (1995Overall, recent ( -2015 retreat rates were higher than at any time in the previous 47 years, but change-point analysis reveals three categories of 15 frontal position change: (i) minimal change followed by steady and continuous retreat, (ii) minimal change followed by a switch to a period of short-lived rapid retreat, (iii) glaciers that underwent cycles of advance and retreat. Furthermore, these categories appear to be linked to the terminus type, with those in category (i) having grounded termini and those in category (ii) characterised by floating ice tongues. We interpret glaciers in category (iii) as surge-type. Glacier geometry (e.g. fjord width and basal topography) is also an important influence on the dynamic re-adjustment of glaciers to changes at their termini. 20Taken together, the loss of several ice tongues and the recent acceleration in the retreat of numerous marine-terminating glaciers suggests northern Greenland is undergoing rapid change and could soon impact on some large catchments that have capacity to contribute an important component to sea level rise.

Velocity response of Petermann Glacier, northwest Greenland to past and future calving events

“…Zacharaie Isstrøm, Hagen Brae: Rignot et al 2001;Hill et al 2017;Mouginot et al 2015), and with Arctic air and ocean temperatures predicted to increase in a warming climate (Gregory et al, 2004), the question remains: at what point will Petermann Glacier lose its ice tongue and how might its complete removal impact on ice dynamics? Petermann's tongue has been retreating from the end of the fjord (∼90 km from the present grounding line) since the beginning of the Holocene (Jakobsson et al, 2018) and currently resides at its most retreated position in recent history (Jakobsson et al, 2018;Falkner et al, 2011;Hill et al, 2018). More recently (2016), another large rift formed across the ice tongue, suggesting another large calving event is imminent.…”

Remote Sensing of Antarctic Glacier and Ice-Shelf Front Dynamics—A Review

“…This cascading effect shows that the buttressing effect of ice shelves and glacier tongues has a major influence on the ice sheet discharge, and thus the Antarctic mass balance. To quantify the contribution of an ice sheet to rising sea levels, it is essential to improve the understanding of iceberg calving and the driving forces behind ice loss [18,46,51], as well as the use of dynamic ice shelf and glacier fronts in mass balance calculations [27] and ice sheet models [52].…”

“…Changes in calving front location are seen as an early sign for further ice dynamical changes [53]. Nevertheless, climate forcing may not be the sole driver, since the "natural" cyclic behavior of calving needs to be considered [17,24,54,55], as well as the type of terminus [28,51]. Recent studies of outlet glaciers in Greenland and Svalbard indicate that ocean forcing and climate forcing at the terminus are the factors principally determining calving changes, rather than ice-sheet dynamics [18,56].…”

Last Glacial ice-sheet dynamics offshore NE Greenland – a case study from Store Koldewey Trough

“…Dowdeswell et al, 1991), Storstrømmen undergoes a slow initiation and termination with a long active surge phase lasting 10 years (Mouginot et al, 2018). The bed topography beneath the ice stream has a reverse slope, resulting in accumulation of subglacial water creating favorable conditions for surges (Mouginot et al, 2018), as well as episodically calving events (Hill et al, 2018).…”

“…The present sub-glacial topography of Storstrømmen consists of a reversed bed slope, accompanied by a floating ice tongue (Hill et al, 2018). Thus, a potential future response to increased ocean warming could result in episodes of rapid retreat as the ice front undergoes thinning and/or ice tongue collapse.…”