December 12, 2017

From a Glaciologists Perspective AGU Day 2

Posted by Mauri Pelto

It has been 30 years since my first experience at the AGU, at that time glaciology and the cryosphere played a small role.  Today that is clearly not the case.  Today just a glimpse of a few of the many interesting glaciers studies are provided to again illustrate the vast array and amazing detail of work being conducted.

Samiah Mustafa, Brown University presented research looking at the ability of a melt model to generate accurate discharge at three watersheds in West Greenland; North River (Thule), Watson River (Kangerlussuaq), and Naujat Kuat River (Nuuk). In each watershed they modeled melt at daily, 5, 10 and 20 day time scales.  They found Nuuk and Thule basins did not do well at a daily time scale, but do capture variability over 5-, 10-, and 20-day means (r2 > 0.7). Results at Watson River were in good agreement at each time scale. Model agreement with river flow data  is reduced during periods of peak discharge, particularly for the exceptional melt and discharge events of July 2012 evident in chart above.

Waldemar Walczowski, Institute of Oceanology Polish Academy of Sciences reported on a study combining glacier retreat and examination of water temperatures in the Hornsund fjord (southern Svalbard), collected under the Polish-Norwegian projects GLAERE and AWAKE-2.  The observed direct contact of warm oceanic water with a glacier’s calving face enhances submarine melting, undercutting and glacier calving.  The turbulent plumes of subglacial meltwater were key in heat transfer and influence glacier retreat. 

Martin Wearing from Lamont Doherty examined the development of crevasses in the past as the Ronne Ice Shelf advanced over the Henry Ice Rise.  The ice shelf thickened and advanced coming in contact with the bedrock high and generating crevasses that first formed around 600o years ago.  They discovered the featured in radar profiles of the ice shelf.  The sequence of crevasse development is seen above.

Morgan Whitcomb from University of Michigan used a simple damage evolution law, based on crevasse distributions as a continuum field to yield estimates of ice shelf calving rates when combined with the Community Ice Sheet Model (CISM).  Their basal melt function enhanced crevasse growth near the ice shelf terminus, leading to increased iceberg calving.  The diagram above shows the model predicts broadly correct calving rates for ice tongues ranging in length from 10 km  on Erebus to over 100 km  on Drygalski Glacier.


Ann Hill, Skidmore college working with the Juneau Icefield Research Programs velocity monitoring program reports on a comparison of velocity and surface elevation on Taku Glacier from 1997-2017.  The velocity on the main profile was consistent, as it had been back to 1950.  The surface elevation has experienced thinning after 1997 after a prolonged period of thickening.  Above are three velocity profiles with red and blue arrows from 1997 and 2017 mostly overlaying each other because velocity did not change.  Above are profiles of height changes for various periods.

 Lu An from UCal Irvine used multiple sources to reconstruct bathymetry glacier bed topography near the grounding line of Sermeq Avangnardleq (AVA) and Sermeq Kujatdleq (KUJ) in central West Greenland.  They used high resolution airborne gravity data from AIRGrav and MultiBeam Echo Sounding data collected in the fjord. The seamless topography obtained across the grounding line reveal the presence of a 300-m sill for AVA that has stabilized its terminus.  For KUJ shown above the sill has helped stabilize the glacier though it has still retreated ~1 km and has led to iceberg stranding.