Biological and Environmental Research - Earth and Environmental System Sciences
Earth and Environmental System Modeling

Morphologic variability of Arctic deltas: Implications for fluxes to the coast

Wednesday, December 13, 2017 - 08:00
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Arctic landscapes are particularly susceptible to climate change, yet Arctic deltas are often understudied due to the inherent difficulties of field-based research. The goal of this study is to characterize and understand the variability in Arctic delta morphology and its possible effects on delivery of material to the coast. We utilized Landsat imagery for six Arctic deltas (Colville, Kolyma, Lena, Mackenzie, Yenisei, and Yukon) to characterize delta morphology, particularly focusing on lakes, channels, and islands. Lake coverage on the deltas varies from 3% (Yenisei) to 19% (Mackenzie). Most delta lakes are round, typical of thermokarst lakes, although some deltas (Lena, Mackenzie, and Yukon) also have more elongate lakes that we interpret to be remnant or abandoned channels. We hypothesize that an abundance of elongate lakes reflects higher rates of channel migration, while a lack of elongate lakes may reflect lower rates of channel migration and therefore elongate lake creation. The Yenisei river, for example, has lower channel migration rates compared to other Arctic rivers and few elongate lakes. To characterize the spatial variability in channel mouths at the coast, we calculated a dimensionless “distribution number” that incorporates channel widths, channel spread, and number of channels. The Lena delta has the highest distribution number, indicating that the Lena more evenly distributes its fluxes across the shoreline. The Kolyma, Mackenzie, and Yenisei have the lowest distribution numbers, which we attribute to the fact that these deltas have grown into confined bays. The Colville, Lena, and Yukon, on the other hand, protrude from the surrounding shoreline, thus facilitating more radial delta growth and channel network expansion. This protrusion also makes the deltas more susceptible to wave and tidal reworking, which could become more dominant as the Arctic warms and the number of ice-free days increases. A more complete analysis of Arctic delta morphologies will improve our understanding of Arctic delta response to climate change.

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