Sediment concentrations and transport in icebergs, Scoresby Sound, East Greeland

• Published in: Hydrological Processes
• Main Authors: Hasholt, Bent, Nielsen, Troels F., Mankoff, Kenneth D., Gkinis, Vasileios, Overeem, Irina
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2022
• Subjects: Greenland; Scoresby; East Greenland; glacier; Scoresby Sound; Tidewater
• Online Access: https://curis.ku.dk/portal/da/publications/sediment-concentrations-and-transport-in-icebergs-scoresby-sound-east-greeland(9d235f5d-f39b-4061-8f44-dbcfca94166c).html; https://doi.org/10.1002/hyp.14668; https://curis.ku.dk/ws/files/319526629/AASA_Processes_2022_Hasholt_Sediments_in_icebergs_and_IRD_transport_Scoresby_Sound_East_Greenland.pdf; https://curis.ku.dk/ws/files/339897396/Sediments_in_icebergsManus190522BH.pdf; https://curis.ku.dk/ws/files/327140495/Sediment_concentrations_and_transport_in_icebergs.pdf

Glaciers erode their beds by abrasion and plucking and entraining sediment on their way downwards driven by gravity. Basal ice becomes a sediment transport agent. To determine glacial transport of sediment, measurements of both the ice flux and its concentration of sediment are needed. Once glaciers reach the ocean, ice and its entrained sediment is released into the ocean by calving. Further transport takes place by icebergs. Quantification of IRD (ice-rafted debris) fluxes, which upon ultimate deposition on the ocean floor is an important climate indicator, becomes even more complicated as icebergs topple and differentially melt while being in transport. While the volume of tidewater glacier ice released by recent calving is quite well constrained by satellite measurements, there is a lack of measurements of the concentration of sediment within the moving ice. Here, we describe a method to collect samples of ice from icebergs systematically for the first time in Greenland together with a strategy to obtain representative samples. Our method is tested in Scoresby Sound, East Greenland in order to describe the transport of sediment into the fjord system related to calving from known glacial source areas. Our data clearly demonstrate that biased and sparse sampling potentially produces unrealistic values of sediment concentrations. Seventy-two samples from 24 icebergs had an average concentration of sediment of 35.5 g/l of ice with a standard deviation of 97%, between the 24 individual icebergs. The origin of the sediment is related to specific source areas. Based on the samples, we present an estimate of the annual transport of sediment out of Scoresby Sound related to calving ~100 (0.3-200) million t yr-1. Finally, we discuss the uncertainties of our estimate.