Abstract

When glaciers and ice sheets release icebergs into the ocean through calving processes, they introduce freshwater into the marine environment, influencing the salt and heat flux in the surrounding area and contributing to ice sheet mass loss. Iceberg keel shape, depth, and density all play crucial roles in determining how fast these icebergs melt and their interactions with fjord stratification and turbulence. In previous studies, iceberg density has been assumed to be the density of solid ice (917 kg/m³), but due to the presence of air bubbles or fractures, the density of many of these icebergs may fall below the solid ice threshold. These factors influence iceberg melting behavior, making it essential to understand both iceberg geometry and density to comprehend local ice-ocean interactions and circulation patterns. While there are many ways to observe the surface of icebergs and their properties above the waterline with satellite remote sensing, measuring iceberg keel shape and estimating density below the waterline is more difficult. Here, I employ ice-penetrating radar to directly investigate submerged iceberg geometries and consider iceberg density variations in Greenland’s fjords.

I analyzed airborne ice-penetrating radar data from NASA’s Operation IceBridge between 2011 and 2017 to distinguish between icebergs calved from ice shelves and those from ice cliffs across 12 fjords in Greenland. Submarine iceberg shape was measured for all icebergs wider than approximately 150 meters and spatial trends across Greenland’s basins were examined. In total, 79 radargrams and 851 icebergs were incorporated into this study. Density is a key assumption in studies of iceberg melt rates. Since many studies rely on specific density values, ensuring they are accurate is important for determining whether their melt rate estimates can be trusted. The results reveal a diverse spatial distribution of iceberg shapes across the basins, including variations in keel depth, aspect ratio, and densities. I observe significant differences in iceberg shape and density depending on whether the iceberg was calved from an ice shelf or ice cliff. Glaciers ending in a cliff face appear to calve narrow but deeper icebergs with lower densities, whereas glaciers terminating in a floating ice shelf appear to calve wider and shallower icebergs with higher densities, suggesting they are less damaged than icebergs that calve from ice cliffs. These findings on submarine iceberg shape and density provide foundational observations that can improve future meltwater flux estimates of icebergs and help us better understand the implications this will have on fjord and glacier systems in a changing climate context.

Advisor

Wiles, Gregory

Department

Earth Sciences

Disciplines

Climate | Earth Sciences | Geology | Glaciology | Oceanography

Keywords

Greenland, Glaciers, Icebergs, Ice-Penetrating Radar, Climate Change, Remote Sensing

Publication Date

2025

Degree Granted

Bachelor of Arts

Document Type

Senior Independent Study Thesis

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© Copyright 2025 Lilly Hinkley