Midway evaluation in Civil Engineering - Andri Gunnarsson

Title: Recent changes in snow and ice in Iceland observed with optical remote sensing

Doctoral candidate: Andri Gunnarsson

Doctoral committee:
Dr. Sigurður Magnús Garðarsson, Professor, Department of Civil and Environmental Engineering, University of Iceland
Dr. Jessica D Lundquist, Professor, Department of Civil and Environmental Engineering, University of Washington
Dr. Óli Grétar Blöndal Sveinsson, Executive Vice President of Research and Development Division at Landsvirkjun
Dr. Tómas Jóhannesson, Coordinator of Glaciological Research, Icelandic Met Office

Abstract
On regional scales, seasonal snow is a vital part of water budgets in mountain and highland catchments where precipitation falls as snow during winter. In Iceland runoff from snow- and glacier-melt is critical for hydropower production and reservoir storage as the energy system is strongly dependent on snowmelt and glacier melt. Over 13 % of the highland area in Iceland is developed for hydropower generation which provides over 72 % of the total average energy produced in Iceland. A system of reservoirs and diversions stores melt water during the melt season in the spring and summer which generally consists of a seasonal snowmelt period (April–June) followed by a glacier melt period (June–September).
The study presents a spatio-temporal continuous data set for snow cover and albedo in Iceland based on the Moderate Resolution Imaging Spectroradiometer (MODIS) from 2000 to 2019. Cloud cover and polar darkness are the main limiting factors for data availability of remotely sensed optical data at higher latitudes providing challenges.
For Icelandic glaciers, surface albedo is the dominating factor governing surface melt annual variability and the importance of correct representation of surface albedo for glacier melt modelling is critical. The analysis shows that the volcanic eruptions in 2010 and 2011 had significant impact on albedo and also had a residual effect in the following years. Furthermore, airborne dust, from unstable sandy surfaces close to the glaciers, is shown to enhance radiative forcing and decrease albedo. A significant positive albedo trend is observed for northern Vatnajökull while other glaciers have non-significant trends for the study period. The results indicate that the high variability in albedo for Icelandic glaciers is driven by climatology, i.e. snow metamorphosis; tephra fall-out during volcanic eruptions and their residual effects in the post-eruption years; and dust loading from widespread unstable sandy surfaces outside the glaciers.
For seasona snow cover, changes over time (trend) analyzed for the 18 years showed a slight increase in average snow cover in spring, likely driven by cold springs in 2013, 2014 and 2015 and extended liquid-phase precipitation in the fall for the same years.
The gap-filled snow cover and albedo products provide a useful tool to monitor and analyze inter-annual variability and long-term trends in Iceland. The methodology applied here can be applied to other satellite sensors such as Sentinel 3 or the Visible Infrared Imaging Radiometer Suite (VIIRS) to extend the temporal range of data beyond the MODIS mission.