Heterogeneous timing of freshwater input into Kobbefjord, a low‐arctic fjord in Greenland. Issue 11 (9th November 2021)

• Record Type: Journal Article
• Authors: Abermann, Jakob; Langley, Kirsty; Myreng, Sille M.; Rasmussen, Kerstin; Petersen, Dorthe
• Is Part Of: Hydrological processes. Volume 35:Issue 11(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-09
• Subjects: freshwater runoff -- Greenland -- river discharge; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14413
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: The majority of freshwater input from Greenland to the global ocean stems from the Greenland Ice Sheet. Currently, almost a quarter of the freshwater flowing from Greenland is derived from catchments that are disconnected from the Greenland Ice Sheet. Despite their importance to the total freshwater flux and influence on fjord geochemistry, there is relatively little monitoring data available for those catchments and therefore the drivers of regional differences in export are largely unknown. We present a dataset of 12 years of discharge of four catchments less than 15 km apart, that are different in size (between 7 and 32 km 2 ), local glacier coverage (4%–11%) and lake cover (0%–5%). They all drain into Kobbefjord, a well‐studied fjord in West Greenland, near Greenland's capital Nuuk. Between catchments, the magnitude of discharge varies at annual, seasonal and sub‐daily timescales, due to differences in physical catchment properties as well as local climate variability. We find that annual specific discharges vary greatly (between 1.2 and 1.9 m/year on a 12‐year average) due to a longitudinal precipitation gradient from West to East caused by different amount of orographic precipitation shading. The seasonal cycle of discharge (amplitude, timing and minimum flow) differs among the sites mainly due to different exposure to solar radiation as a driver for major snowmelt; the small ice coverage in the catchments plays only a minor role in discharge variability. Dry years generally increase the relative differences in annual specific discharge and no significant temporal trends have been found in the studied catchments. On a sub‐daily timescale, the difference in timing of maximum discharge during fair‐weather days (>80% maximum solar radiation and no precipitation) ranged between 7 and 12 h, which is attributed to differences between the presence and elevation of lakes among the catchments. The response of discharge to major precipitation events is discussed, where a delay of between 5 and 7 h is found for the catchments that do not contain lakes near the gauge. Abstract : Observational data of freshwater input into a low‐Arctic Fjord in Greenland shows strong gradients in discharge totals for four stations less than 15 km apart, yet no temporal trend. Drivers for spatial variability are dependent on the temporal scale: for annual totals, orographic shading plays the major role, while for the diurnal cycle and the heavy precipitation events catchment characteristics and particularly lake coverage are decisive.