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The effect of warming climate on nutrient and solute export from the Greenland Ice Sheet

J.R. Hawkings1,

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK

J.L. Wadham1,

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK

M. Tranter1,

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK

E. Lawson1,2,

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK
2School of Geography, University of Nottingham, University Park, Nottingham, NG7 2RD, UK

A. Sole3,

3Department of Geography, The University of Sheffield, Western Bank, Sheffield, S10 2TN, UK

T. Cowton3,4,

3Department of Geography, The University of Sheffield, Western Bank, Sheffield, S10 2TN, UK
4School of Geoscience, University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, UK

A.J. Tedstone4,

4School of Geoscience, University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, UK

I. Bartholomew4,

4School of Geoscience, University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, UK

P. Nienow4,

4School of Geoscience, University of Edinburgh, Drummond Street, Edinburgh, EH8 9XP, UK

D. Chandler1,

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK

J. Telling1

1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1SS, UK

Affiliations  |  Corresponding Author  |  Cite as

Cite this letter as: Hawkings, J.R., Wadham, J.L., Tranter, M., Lawson, E., Sole, A., Cowton, T., Tedstone, A.J., Bartholomew, I., Nienow, P., Chandler, D., Telling, J. (2015) The effect of warming climate on nutrient and solute export from the Greenland Ice Sheet. Geochem. Persp. Let. 1, 94-104.

Geochemical Perspectives Letters v1, n1  |  doi: 10.7185/geochemlet.1510
Received 10 March 2015  |  Accepted 19 June 2015  |  Published 23 June 2015
Copyright © 2015 European Association of Geochemistry


Figure 1 Field site and basic hydrological data. (a) Leverett Glacier with the snowline transect used to determine the point where snow covers the ice surface, derived from MODIS imagery. Dashed lines represent elevation contours. The catchment area was determined from a surface digitial elevation model (Palmer et al., 2011

Palmer, S., Shepherd, A., Nienow, P., Joughin, I. (2011) Seasonal speedup of the Greenland Ice Sheet linked to routing of surface water. Earth and Planetary Science Letters 302, 423-428.

). (b) Leverett Glacier meltwater discharge (Table 1) versus modelled Greenland Ice Sheet runoff (Tedesco et al., 2013

Tedesco, M., Fettweis, X., Mote, T., Wahr, J., Alexander, P., Box, J.E., Wouters, B. (2013) Evidence and analysis of 2012 Greenland records from spaceborne observations, a regional climate model and reanalysis data. Cryosphere 7, 615-630.

). (c) Leverett Glacier snowline; open circles represent observed position; connecting lines are linear estimates of retreat, interpolated between the measurements. Estimated catchment extent is represented by the dotted line at ~80 km.
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Table 1 Flux and hydrological data.
 Year
 Units2009201020112012
Greenland Ice Sheet runoff * km3348559466665
Leverett Glacier discharge km30.941.791.12.03
Snowline above catchmentest. days451007385
Snowline retreat from marginkm125135135149
Solute Flux eq3.0 × 1085.6 × 1083.2 × 1085.6 × 108
Sediment Flux t
3.7× 1062.6 × 1063.0 × 1062.2 × 106
Dissolved inorganic nitrogen †t
25462648
Dissolved silica †t
130230120230
Dissolved inorganic phosphorus†t
6.2126.712
Dissolved inorganic nitrogen ‡t
22412547
Dissolved silica ‡t
110220130240
Dissolved inorganic phosphorus‡t
7.8158.916
Exchangeable NH4**t
19-5813-4115-4711-35
Amorphous silica**t
18.000-44.00012.000-31.00014.000-36.00011.000-26.000
NaOH extractable phosphorus**t
20-130 14-9216-11012-78

All estimates are shown to Decimal Day 230/231, i.e. 17 August.
Estimates are reported with 2 significant digits.
eq = molar equivalent
t = tons of dry element
Snowline: the boundary where snow covers the underlying ice. Down glacier from this point is exposed ice, where the snow cover has melted.
* Greenland Ice Sheet runoff estimates from Tedesco et al. (2013) Tedesco, M., Fettweis, X., Mote, T., Wahr, J., Alexander, P., Box, J.E., Wouters, B. (2013) Evidence and analysis of 2012 Greenland records from spaceborne observations, a regional climate model and reanalysis data. Cryosphere 7, 615-630. .
** Sediment fluxes given as range based on minimum and maximum extractable nutrient concentrations.
† Fluxes estimated with electrical conductivity.
‡ Fluxes estimated using discharge weighted mean.

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Figure 2 Cumulative solute and sediment flux. (a) Solid lines show solute flux (Ca2+, Mg2+, K+, Na+, Cl-, SO42-, HCO3-); dashed lines represent the estimated portion originating from supraglacial meltwater (right axis). (b) Cumulative particle borne flux. (c) Cumulative meltwater discharge. Day 230 (dashed line) was the limit of the dataset interpretation. Values at the dashed line correspond to data presented in Table 1 and Figure 1b.
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Figure 3 Estimated nutrient flux. Minimum (left column), mean (middle) and maximum (right) possible values give an impression of the range for phosphate, silicate and nitrogen compounds. Dissolved flux was determined using the electrical conductivity correlation.
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Supplementary Figures and Tables



Figure S-1 Leverett Glacier discharge hydrographs and electrical conductivity. Shaded areas in the discharge plots show when discharge exceeded 200 m3 sec-1. The dashed line represents the cut off date used for flux estimates.
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Figure S-2 An example of the MODIS satellite imagery used to determine snowline extent. Data are from surface reflectance bands 1-2 (Product Number MOD09GQ). Leverett Glacier moves from east to west. The estimated catchment area is outlined in black (Palmer et al., 2011

Palmer, S., Shepherd, A., Nienow, P., Joughin, I. (2011) Seasonal speedup of the Greenland Ice Sheet linked to routing of surface water. Earth and Planetary Science Letters 302, 423-428.

) and the snowline transect is displayed by the red dotted line (space between each dot = 5 km). False colour imaging differentiates between snow (dark blue) and ice (light blue). The margin of the ice sheet is evident at the border of the red colouring (black arrow). The blue dashed line represents the interpreted position of the snowline. The image displayed is from 21 July 2012. Fig. 1a provides more information about the catchment.
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Figure S-3 Regression plots for major ions as a function of electrical conductivity. Shaded blue lines represent the standard error (σ, also written in the top left of plots). The 2011 regression plot (bottom left), which encompasess data from 2009, 2010 and 2012, is magnified to demonstrate the linear relationship of electrical conductivity with major ions in the dilute waters.
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Figure S-4 Comparison of regression plots for the major ions for 2009, 2010 and 2012, where data are available. The differences in the regression equations used to determine major ion concentrations are very small.
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Figure S-5 Temporal variation in meltwater discharge and estimated solute flux. Coloured lines indicate solute flux calculated by the EC based method (eq min-1), and black lines, meltwater discharge (m3 min-1), during the 2009-2012 melt seasons. Shaded areas correspond to meltwater pulse events. These are associated with spring events, i.e. the annual opening of the subglacial drainage system, or rapid drainage of meltwater from supraglacial lake drainage events. These meltwater pulses flush concentrated waters from the subglacial drainage system (Bartholomew et al., 2011

Bartholomew, I., Nienow, P., Sole, A., Mair, D., Cowton, T., Palmer, S., Wadham, J. (2011) Supraglacial forcing of subglacial drainage in the ablation zone of the Greenland ice sheet. Geophysical Research Letters 38, L08502.

and Hawkings et al., 2014

Hawkings, J.R., Wadham, J.L., Tranter, M., Raiswell, R., Benning, L.G., Statham, P.J., Tedstone, A., Nienow, P., Lee, K., Telling, J. (2014) Ice sheets as a significant source of highly reactive nanoparticulate iron to the oceans. Nature Communications 5.

).
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Figure S-6 Regression plots for nutrient concentrations as a function electrical conductivity. The regression plots for Si and PO43- represent early (blue) versus later season (red) hydrological and associated biogeochemical changes. Early season regressions are applied to time points before Day 153 in 2009, Day 128 in 2010, Day 160 in 2011 and Day 150 in 2012, which are before the initial change in drainage hydrology occurred, i.e. the spring event (Figs S-1 and S-5). Shaded areas show associated standard error.
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