Spatiotemporal distributions of icebergs in a temperate fjord: Columbia Fjord, Alaska

• Published in: The Cryosphere
• Main Authors: S. U. Neuhaus, S. M. Tulaczyk, C. Branecky Begeman
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2019
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Greenland; glacier; glaciers; The Cryosphere; Alaska
• Online Access: https://doi.org/10.5194/tc-13-1785-2019; https://doaj.org/article/3108520b7c364560a61d55e194ddbdab

Much of the world's ice enters the ocean via outlet glaciers terminating in fjords. Inside fjords, icebergs may affect glacier–ocean interactions by cooling incoming ocean waters, enhancing vertical mixing, or providing back stress on the terminus. However, relatively few studies have been performed on iceberg dynamics inside fjords, particularly outside of Greenland. We examine icebergs calved from Columbia Glacier, Alaska, over 8 months spanning late winter to mid-fall using 0.5 m resolution satellite imagery, identifying icebergs based on pixel brightness. Iceberg sizes fit a power-law distribution with an overall power-law exponent, m , of <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo>-</mo><mn mathvariant="normal">1.26</mn><mo>±</mo><mn mathvariant="normal">0.05</mn></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="64pt" height="10pt" class="svg-formula" dspmath="mathimg" md5hash="f35c24ab1184fe0ceb4a3ef4dcd5d0ae"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-13-1785-2019-ie00001.svg" width="64pt" height="10pt" src="tc-13-1785-2019-ie00001.png"/></svg:svg> . Seasonal variations in the power-law exponent indicate that brittle fracture of icebergs is more prevalent in the summer months. Combining our results with those from previous studies of iceberg distributions, we find that iceberg calving rate, rather than water temperature, appears to be the major control on the exponent value. We also analyze icebergs' spatial distribution inside the fjord and find that large icebergs (10 000–100 000 m 2 cross-sectional area) have low spatial correlation with icebergs of smaller sizes due to their tendency to ground on shallow regions. We estimate the surface area of icebergs in contact with incoming seawater to be <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" ...