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theses

In the region of Earth most sensitive to climate change, spring snowmelt serves as a measurable indicator of climate change and plays a strong role in the feedbacks that amplify Arctic warming. These feedbacks are strongest over sea ice and the Greenland ice sheet (GrIS) as these surfaces continue to melt through the summer and potentially impact one another. The first component of this study characterizes the snow melt season and attributes melt onset both at a hemispheric scale and regionally in northern Canada. Analysis is then expanded to the melt onset date (MOD) on sea ice and the GrIS where covariability is addressed extending into the summer melt season. MOD and sea ice concentration (SIC) data are obtained from passive microwave satellite datasets, while NASA’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) provides energy balance and meteorological fields with primarily meltwater production used as output from a regional climate model (Modèle Atmosphérique Régional, MAR) for the period 1979 - 2013. Across much of the Northern Hemisphere, energy advection plays a larger role in melt onset in regions where snow begins melting in March and April, while shortwave fluxes have a greater influence where the MOD occurs in May and June. As the MOD arrives earlier, this implies that there is a potential shift in snow melt drivers toward those involved in advective processes. Comparable results are found in the regional study, where melt is controlled more by advective energy where melt onset begins sooner, compared to higher levels of radiative energy further north. Analysis of the remainder of the Arctic finds strong covariability among Greenland meltwater production, 500 hPa geopotential heights, and SIC, particularly in Baffin Bay, Fram Strait, and Beaufort Sea early in the summer. Most of this covariance is likely due to simultaneous influence of the atmospheric circulation anomalies, though there may be a local influence from Baffin Bay to the GrIS. Height anomalies from Greenland to Beaufort Sea favor the largest anomalies in meltwater production, and positive height anomalies in this configuration have shown the greatest increase in frequency of any pattern in the study period.

ETD_6366

Ph.D.

Includes bibliographical references

by John Mioduszewski

doi:10.7282/T3VQ34J2

ETD doctoral

The author owns the copyright to this work.