Date of Award

Summer 2021

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Ocean and Earth Sciences

Committee Director

Victoria J. Hill

Committee Member

Richard C. Zimmerman

Committee Member

Sophie Clayton

Abstract

As the Arctic experiences consequences of climate change, a shift from thicker, multi-year ice to thinner, first-year ice has been observed. First-year ice is prone to extensive pools of meltwater (“melt ponds”) forming on its surface, which enhance light transmission to the ocean. Changes in the timing and distribution of melt pond formation and associated increases in under-ice light availability are the primary drivers for seasonal progression of water column primary production and warming. Observations of melt pond development and distribution require meter scale resolution and have traditionally been limited to airborne images. However, recent advances in high spatial resolution satellites now allow for observations of individual melt ponds from space.

Images of pack ice in the Chukchi Sea during 2018 obtained from WorldView satellite systems showed minimal melt pond coverage in June, with a rapid increase in late June, leading to saturated and flooded ice floes by mid-July. Cumulative hours above freezing (air temperature) was a stronger predictor for pond development than daily average values of temperature and irradiance and was well represented by a logistic growth curve.

Size distributions (normalized to total pond area) of melt pond area was dominated by small (≤10 m2) ponds at the onset of ponding, shifting towards medium sized ponds (mode of 100 to 1,000 m2) as surface melt progressed. Late in the summer when ice flows were saturated with ponds, the distribution was skewed towards a handful of very large ponds nearing 1,000,000 m2, connected by channels which created a myriad of complex shapes.

A primary production model driven by under-ice light intensity estimated from our classified images revealed that initial small increases in melt pond fraction have a large impact on potential under-ice chlorophyll growth and carbon uptake, eventually trending towards a saturating upper limit as ponds continued to spread. Results shown here offer novel insights into melt pond growth and distribution, along with estimates of how ponding impacts primary production. These conclusions showcase physical, observable consequences of an Arctic Ocean dominated by thin, first-year ice, and can be employed to advise future efforts in Arctic modeling.

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DOI

10.25777/n8vk-pn68

ISBN

9798460433605

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