Date of Award

Spring 1-1-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Scott Palo

Second Advisor

James Maslanik

Third Advisor

Mark Tschudi

Fourth Advisor

Lakshmi Kantha

Fifth Advisor

John Cassano

Abstract

The Arctic seasonal ice zone undergoes dramatic changes throughout the year. In the summer, ice cover melts off, leaving the ocean surface exposed to the atmosphere. Incident solar radiation warms the surface mixed layer. At the end of the summer season, the mixed layer must then cool to the freezing point in order for ice to form at the surface. This thesis explores the impact of that heat throughout the annual cycle, but especially on first-year ice growth. Through analysis of CTD profiles and buoy data, it is found that summer heat gets into the summer halocline, where it is trapped through the fall season cooling process. The mixed layer heat (estimated from an empirical relationship derived from direct measurements and atmospheric and geographic parameters along with sea surface temperatures) is well correlated with freeze-up date. The results presented herein suggest that delayed freeze-up does result in thinner ice cover at the end of the winter season, in part because the maximum ice growth rate is consistent (approximately 12 cm/day) between observations from Antarctic polynyas with exceptionally high ice production and the few observations that exist in the Arctic. Finally, from analysis of end-of-season first year ice thickness distributions, it is clear that the summer heat trapped in the summer halocline is released over the course of the winter, limiting ice growth in addition to that caused by the delay in freeze-up. In all, it is likely that as the Arctic becomes increasingly dominated by first-year ice, the thinning trend will continue though at a slower rate than in the current transition from multi- to first-year ice cover.

Comments

Sixth advisor: John Cassano.

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