Sediment plumes as a proxy for local ice-sheet runoff in Kangerlussuaq Fjord, West Greenland

McGrath, Daniel; Steffen, Konrad; Overeem, I.; Mernild, Sebastian H.; Hasholt, Bent; Broeke, Michiel van den

doi:10.3189/002214310794457227

Cited by 52 publications

(66 citation statements)

References 56 publications

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“…Previous plume metrics used to study meltwater discharge, namely plume area and plume length (Dowdeswell and Cromack 1991), have a fairly good relationship with meltwater run-off at land-terminating glaciers (Chu et al 2009;McGrath et al 2010) but do not display the same relationship at tidewater glaciers (Chu et al 2012;Tedstone and Arnold 2012). This is likely due to the plume itself being influenced by fjord stratification, circulation, and depth.…”

Section: Calculating Surface Sediment Loadmentioning

confidence: 79%

“…The spatial variability of plumes, as well as the difference in the relationship between total surface sediment load and constructed PDDs in the two field locations (Figure 5), highlights the importance of fjord geometry, ocean stratification, sediment supply, and plume dynamics in different fjord systems. These factors affect the size, depth, and concentration of a sediment plume and necessitate the development of site-specific relationships, potentially even season-specific relationships, between total surface sediment load and meltwater discharge (variability also noted in McGrath et al 2010;Tedstone and Arnold 2012;Hudson et al 2014). While these calculations of total surface sediment load do not give the full sediment load across all depths, nor a direct measurement of meltwater discharge, the change in total surface sediment load could indicate discharge events or periods of time with increased or decreased meltwater run-off for individual drainage basins.…”

Section: Total Surface Sediment Loadmentioning

confidence: 99%

“…Landsat-8 has a 16 days repeat orbit; however, at the high latitude of these study sites (about 78°N), repeat satellite coverage is between 2 and 4 days. While not as high of temporal resolution as MODIS (previously used by Chu et al 2009;McGrath et al 2010;Chu et al 2012;Tedstone and Arnold 2012;Hudson et al 2014;Schild, Hawley, and Morriss 2016), we chose to use the Landsat-8 imagery because its higher spatial resolution (30 m compared to MODIS 250 or 500 m) better resolves the smaller glaciers and fjords of our study sites.…”

Section: Landsat-8 Surface Reflectancementioning

confidence: 99%

“…Lower SSC values also mean that a majority of the sediment plume is below an established reflectance detection threshold; therefore, any measurements of plume length or area would be underestimates. However, sediment plumes remain an indicator of subglacially transported meltwater and capture meltwater discharge, thereby integrating poorly constrained processes of meltwater refreezing and water storage (McGrath et al 2010). Sediment plumes have been used as a proxy for meltwater run-off at land-terminating glaciers (Gurnell and Warburton 1990;Chu et al 2009;McGrath et al 2010) and can be used at tidewater glaciers if a new metric can be established to quantify sediment in plumes at tidewater margins.…”

Section: Introductionmentioning

confidence: 99%

“…This study focuses on the suspended sediment concentration (SSC) of subglacial meltwater plumes; we therefore chose wavelengths optimal for detecting minerals. In less turbid waters, the wavelength can be restricted to visible bands (Binding, Bowers, and Mitchelson-Jacob 2005) as early studies were successful using the MODIS (Moderate Resolution Imaging Spectroradiometer) red band (620-670 nm, 250 m) to calculate SSC (Miller and McKee 2004;Chu et al 2009;McGrath et al 2010;Chu et al 2012;Tedstone and Arnold 2012). As turbidity increases and sediment concentrations reach values >80 mg l the surface reflectance saturates (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Schild

Hawley

Chipman

et al. 2017

International Journal of Remote Sensing

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Marine-terminating outlet glaciers discharge mass through iceberg calving, submarine melting, and meltwater run-off. While calving can be quantified by in situ and remote-sensing observations, meltwater run-off, the subglacial transport of meltwater, and submarine melting are not well constrained due to inherent difficulties observing the subglacial and proglacial environments at tidewater glaciers. Remote-sensing and in situ measurements of surface sediment plumes, and their suspended sediment concentration (SSC), have been used as a proxy for glacier meltwater run-off. However, this relationship between satellite reflectance and SSC has predominantly been established using land-terminating glaciers. Here, we use two Svalbard tidewater glaciers to establish a well-constrained relationship between Landsat-8 surface reflecance and SSC and argue that it can be used to measure relative meltwater runoff at tidewater glaciers throughout a summer melt season. We find the highest correlation between SSCs and Landsat-8 surface reflectance by using the red + NIR band combination (r 2 = 0.76). The highest correlation between SSCs and in situ field spectrometer measurements is in the 740-800 nm wavelength range (r 2 = 0.85), a spectral range not currently measured by Landsat. Additionally, we find that in situ and Landsat-8 measurements for surface reflectance of SSCs are not interchangeable and therefore establish a relationship for each detection method. We then use the Landsat-8 relationship to calculate total surface sediment load, finding a strong correlation between total surface sediment load and a proxy for meltwater run-off (r 2 ≥ 0.89). Our results establish a new metric to calculate SSCs from Landsat-8 surface reflectance and demonstrate how the SSC of subglacial sediment plumes can be used to monitor relative seasonal meltwater discharge at tidewater glaciers. ARTICLE HISTORY

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Section: Calculating Surface Sediment Loadmentioning

confidence: 79%

Section: Total Surface Sediment Loadmentioning

confidence: 99%

Section: Landsat-8 Surface Reflectancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Schild

Hawley

Chipman

et al. 2017

International Journal of Remote Sensing

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Exploring the Potential Impact of Greenland Meltwater on Stratification, Photosynthetically Active Radiation, and Primary Production in the Labrador Sea

et al. 2018

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In July 2012, the surface of the Greenland Ice Sheet (GrIS) melted to an extent unprecedented over the last 100 years; we questioned the potential for such an extreme melt event to impact marine phytoplankton offshore. We hypothesized that stratification from meltwater could reduce light limitation for phytoplankton, and used a suite of numerical models to quantify the impact for 2003–2012. Because much of the 2012 meltwater discharged from southern Greenland, our study focused on the southwestern and southeastern coasts of Greenland, and the Labrador Sea. A 1‐D phytoplankton model used output from a Regional Ocean Modeling System (ROMS) coupled with a Regional Climate Model and a hydrological model of meltwater from runoff sources on the ice sheet, peripheral glaciers, and tundra. ROMS was run with and without meltwater to test the sensitivity of phytoplankton photosynthetic rates to the meltwater input. With meltwater, the pycnocline was shallower during late summer and early fall and thus light limitation on photosynthesis was reduced. Averaged over all years, added meltwater had the potential to increase gross primary production by 3–12% in the summer (July–August), and 13–60% in the fall (September–October). This meltwater effect was amplified when light was more limiting, and thus was greatest in the fall, under cloudier conditions, with higher self‐shading, and with more light‐sensitive phytoplankton groups. As the GrIS melt is projected to increase, late summer primary production in this region has the potential to increase as well, which could constitute an important biosphere response to high‐latitude climate change.

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Contemporary glacigenic inputs to the dust cycle

Bullard

2012

Earth Surf Processes Landf

104

103

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The importance of glacigenic dust in the Earth's system during glacial periods is widely acknowledged. Under contemporary conditions, the world's largest dust sources are in low‐lying, hot, arid regions and this is where most aeolian research is focused. However the processes of dust production and emissions are still operating in cold climate regions, particularly in proglacial areas. This paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle. It focuses on how elements in the glacial and aeolian geomorphic sub‐systems interact to determine the magnitude, frequency and timing of aeolian dust emissions, and on feedback mechanisms between the systems. Where they have been measured, dust emission intensity and deposition rates in glacierised catchments are very high, in some cases far exceeding those in lower latitudes, however, few studies span long time scales. The impact of future glacier retreat on the balance between sediment supply, availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered. This balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths, which promote dust emissions, and patterns and rates of soil development and vegetation succession on recently‐deglaciated terrain which protect sediments from deflation. Retreat of the Antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non‐glacigenic sources in the southern hemisphere. Copyright © 2012 John Wiley & Sons, Ltd.

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Sediment plumes as a proxy for local ice-sheet runoff in Kangerlussuaq Fjord, West Greenland

Cited by 52 publications

References 56 publications

Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Quantifying suspended sediment concentration in subglacial sediment plumes discharging from two Svalbard tidewater glaciers using Landsat-8 and in situ measurements

Exploring the Potential Impact of Greenland Meltwater on Stratification, Photosynthetically Active Radiation, and Primary Production in the Labrador Sea

Contemporary glacigenic inputs to the dust cycle

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