Glacier Surface Melt Characterization and Trend Analysis in Novaya Zemlya and Severnaya Zemlya from Microwave Datasets
Ramage, Joan; Zhao, Meng; Semmens, Kathryn A.
Lehigh University, UNITED STATES
The glacierized high arctic archipelagoes of Severnaya Zemlya and Novaya Zemlya, Russia (71°~81°N, 55°~105°E) are vulnerable to rapid high latitude climate change. We examine the recent glacier surface melt trends on their low altitude, high latitude small ice caps. The timing and spatial variability of snow melt onset, duration and intensity are key factors influencing mass balance and the ice marginal hydrological system as well as important indicators of glacial response to anthropogenic and natural forcings. Characterization and trend analysis of glacier melt behaviors help to assess the mass loss rate under recent Arctic climate change. However, due to the harsh environment, long term records of glaciological data for RHA are limited, necessitating the application of remotely sensed data. The high sensitivity to liquid water and the ability to penetrate non-precipitating clouds enables microwave remote sensing to detect glacier surface melt. The appearance of melt water in snow dramatically decreases the returned scatterometer radar signal from active microwave sensors and sharply augments passive microwave emission. Based on this feature, we combined resolution-enhanced ERS-1/2 C-band (1992-2000), QuikSCAT Ku-band (2000-2009), ASCAT C-band (2009-2011) scatterometer data and SSM/I 37 GHz (1995-2007), AMSR-E 36.5 GHz (2003-2011) vertically polarized passive microwave products from Brigham Young University and analyzed recent decadal glacier surface melt trends with a spatial resolution of 8.9 km. We concatenated passive microwave derived melt behaviors by overlapping years and compared to scatterometer derived melt records. Cross-validation shows melt timing to be consistent between the active and passive sensors. Trend analysis (Yá < 0.01) reveals that the average glacier surface melt onset date occurs earlier by approximately 0.73 days/year in Severnaya Zemlya from 1992 to 2012 which outpaced the mean rate of increase in the pan-Arctic (0.5 days/year from 1979 to 2008). Its melt season duration is also increasing at a rate of ~0.63 days/year (Yá < 0.05) from 1995 to 2011. Although Novaya Zemlya is experiencing large interannual variability in melt onset, annual total melt days are increasing. Linear regression (Yá < 0.01) shows that annual minimum regional sea ice extent is negatively related to total number of melt days for both islands, with the exception of 2010, an anomalously warm year in the Novaya Zemlya analysis. Surrounded by ocean water, these high arctic glaciers are expected to be more vulnerable to the continuously diminishing summer sea ice extent, the associated air temperature increase and amplifying positive albedo feedback.