News & Events

Grad student talk - Has increased runoff from the Greenland Ice Sheet altered the SCC of fjords?

Thursday, August 29, 2013, 4:30PM - 5:30PM

Speaker

Ben Hudson

Location:

RL-1 room 269

Full title: Has increased runoff from the Greenland Ice Sheet altered the SCC of fjords? An investigation with MODIS.

Abstract: The Greenland Ice Sheet (GrIS) is the largest land-bound ice mass in the northern hemisphere. In the recent past (1992 to 2011) it is estimated the GrIS lost approximately 142 ±49 gigatons of mass per year and models have suggested that fresh water runoff from the GrIS has increased three percent per year from 1990 to 2007. We test the hypothesis that increases in freshwater discharge from the GrIS to coastal fjords has also caused an increase in fjord suspended sediment concentration (SSC).

We collected > 140 surface water samples from six river plumes in three fjords in Southwest Greenland over the summers of 2008, 2010, 2011 and 2012. The data was used to develop an algorithm to retrieve suspended sediment concentration (SSC) from NASA Moderate Resolution Imaging Spectrometer (MODIS) band one and two reflectance values.

We applied this suspended sediment retrieval algorithm to all cloud-free pixels in the 13-year long MODIS Terra image archive to make estimates of how suspended sediment concentrations in each fjord varied on year-to-year time scales.

We find that yearly mean fjord SSC has not increased in a statistically significant way, with the exception of one river. However, we do find that a positive, statistically significant trend in high SSC events exists in all by one river plume, indicating that more extreme pulses of sediment may be entering Greenland fjords.  We also find that often plume SSC does not vary in synchronicity from plume to plume, even in catchments adjacent to each other.