A century of geometry and velocity evolution at Eqip Sermia, West Greenland

Abstract

ABSTRACT. Rapid dynamic changes of ocean-terminating outlet glaciers of the Greenland ice sheet are related to atmospheric and oceanic warming but the detailed link to external forcing is not well understood. Observations show high variability in dynamic changes and are mainly limited to the past three decades with dense satellite observations. Here we compile a long-term record of dynamic changes of Eqip Sermia Glacier, West Greenland. Starting in 1912, we combine historical measurements of terminus positions, ice-surface elevation and flow velocity together with more recent in-situ and remote-sensing observations. In the 20th century, the glacier underwent small variations in terminus position and flow speed. Between 2000 and 2003, the terminus retreated substantially, but stabilized thereafter. In 2009, the northern terminus lobe started to retreat very rapidly; the southern lobe collapsed in 2013. The present terminus position, which has retreated by 4 km since 1920, is unprecedented in the historical record. Flow velocities were relatively stable until 2010. The recent acceleration reached threefold velocities in 2014 and rapidly affected the whole terminus region up to 15 km inland. Comparison with forcings from the atmosphere and the ocean over the past century shows that no dominant cause can be identified, and that local effects of bed geometry modulate the glacier response.

Multi-method observation and analysis of a tsunami caused by glacier calving

“…This water depth estimate agrees well with depth soundings in the fjord which are mostly in the range 100-150 m (Lüthi et al, 2016).…”

“…The distance from the terminus where the maximum wave amplitude is attained, however, is calculated to 330-390 m, whereas the observations yield ∼ 260 m. This difference might be due to a deepening of the bathymetry away from the glacier terminus (Lüthi et al, 2016), and thus reduced wave heights there. An alternative formulation for the maximum wave amplitude in 3-D (Eq.…”

“…Since collapses of the 200 m high glacier front cause the tsunami waves, we can infer that such a high ice cliff is a very recent phenomenon. Indeed, throughout the documented history of Eqip Sermia (since 1912), the maximum cliff height of the glacier was about 50 m (Lüthi et al, 2016), from which smaller tsunamis were triggered.…”

“…The terminus area is about 4 km wide and terminus flow speed was about 3 m day −1 during the last century, corresponding to a calving flux of ∼ 0.8 km 3 a −1 (Bauer, 1968). After a century of slowly varying terminus positions, a slow retreat and acceleration started in 2000, and flow velocities accelerated to 14 m day −1 in 2014 (Lüthi et al, 2016). In 2014, the calving front reached 150-200 m height in the northern terminus lobe.…”

Geometric Controls on Tidewater Glacier Retreat in Central Western Greenland

“…This produces more rapid retreat for some parts of the terminus and thus changes in the terminus shape through time. This is most obvious for KSS and EQI (Lüthi et al, ; Figures S12 and S41 and Movies S2 and S3 in the supporting information), but generally most glaciers appear to have more flat or convex termini when they are stable (e.g., STR and KAS) and more concave termini shapes when they are retreating (e.g., UMI and SIL).…”