Sediment transport by Greenland’s icebergs

TL;DR

Greenland's icebergs transport a large amount of sediment to fjords each year, playing a key role in marine ecosystems and sediment cycles.

Contribution

Quantifies iceberg sediment transport and its role in Greenland's sediment budget using field data and numerical modeling.

Findings

Icebergs export 454 Mt a−1 of ice-rafted debris (IRD) from Greenland.

IRD accounts for up to one-third of Greenland’s total sediment transport.

A long-tailed distribution of sediment concentrations was observed in debris-rich icebergs.

Abstract

Ice-rafted debris (IRD) from Greenland’s tidewater glaciers provides key inputs to biogeochemical cycles, sequesters sediment in fjords, and leaves evidence of paleoclimate conditions. Previous work has shown that most IRD is entrained in basal ice, but studies have yet to translate this process knowledge into predictions of IRD export. Here, we combine field data and numerical models to quantify sediment transport in basal ice and estimate IRD fluxes. We present 210 samples of debris-rich icebergs, collected from three fjord systems, showing a long-tailed distribution of sediment concentrations between 0.1% and 45% by mass (3.48% median). Then, we develop a numerical process model of erosion and entrainment to predict the thickness of debris-rich ice layers and the IRD flux from each outlet. Across our selected fjords, we show a first-order relationship between a catchment’s ice yield and sediment yield. By extrapolating this relationship across Greenland’s marine-terminating outlets, we estimate that icebergs export 454 Mt a−1 of IRD (with a 95% confidence interval from 292 to 716 Mt a−1), representing up to one-third of Greenland’s total sediment transport. Our results demonstrate the significant role of icebergs in Greenland’s sediment budget, improving our understanding of how sediment export from glaciers and ice sheets will change under a warming climate.

Greenland’s icebergs transport 450 megatonnes of sediment to its fjords each year, representing one-third of the ice sheet’s total sediment export. This ice-rafted debris builds shoals at tidewater glacier margins and provides key nutrients for marine ecosystems.

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