Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet
Rapid changes in thickness and velocity have been observed at many marine-terminating glaciers in Greenland, impacting the volume of ice they export, or discharge, from the ice sheet. While annual estimates of ice-sheet-wide discharge have been previously derived, higher-resolution records are requi...
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ftcopernicus:oai:publications.copernicus.org:tc71066 2023-05-15T16:21:24+02:00 Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet King, Michalea D. Howat, Ian M. Jeong, Seongsu Noh, Myoung J. Wouters, Bert Noël, Brice Broeke, Michiel R. 2018-12-03 application/pdf https://doi.org/10.5194/tc-12-3813-2018 https://tc.copernicus.org/articles/12/3813/2018/ eng eng doi:10.5194/tc-12-3813-2018 https://tc.copernicus.org/articles/12/3813/2018/ eISSN: 1994-0424 Text 2018 ftcopernicus https://doi.org/10.5194/tc-12-3813-2018 2020-07-20T16:23:01Z Rapid changes in thickness and velocity have been observed at many marine-terminating glaciers in Greenland, impacting the volume of ice they export, or discharge, from the ice sheet. While annual estimates of ice-sheet-wide discharge have been previously derived, higher-resolution records are required to fully constrain the temporal response of these glaciers to various climatic and mechanical drivers that vary in sub-annual scales. Here we sample outlet glaciers wider than 1 km ( N =230 ) to derive the first continuous, ice-sheet-wide record of total ice sheet discharge for the 2000–2016 period, resolving a seasonal variability of 6 %. The amplitude of seasonality varies spatially across the ice sheet from 5 % in the southeastern region to 9 % in the northwest region. We analyze seasonal to annual variability in the discharge time series with respect to both modeled meltwater runoff, obtained from RACMO2.3p2, and glacier front position changes over the same period. We find that year-to-year changes in total ice sheet discharge are related to annual front changes ( r 2 =0.59 , <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>p</mi><mo>=</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="44pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="ffcc76c21433832f54aa79d0cec7f6aa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-12-3813-2018-ie00001.svg" width="44pt" height="15pt" src="tc-12-3813-2018-ie00001.png"/></svg:svg> ) and that the annual magnitude of discharge is closely related to cumulative front position changes ( r 2 =0.79 ), which show a net retreat of >400 km, or an average retreat of >2 km, at each surveyed glacier. Neither maximum seasonal runoff or annual runoff totals are correlated to annual discharge, which suggests that larger annual quantities of runoff do not relate to increased annual discharge. Discharge and runoff, however, follow similar patterns of seasonal variability with near-coincident periods of acceleration and seasonal maxima. These results suggest that changes in glacier front position drive secular trends in discharge, whereas the impact of runoff is likely limited to the summer months when observed seasonal variations are substantially controlled by the timing of meltwater input. Text glacier Greenland Ice Sheet Copernicus Publications: E-Journals Greenland The Cryosphere 12 12 3813 3825 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Rapid changes in thickness and velocity have been observed at many marine-terminating glaciers in Greenland, impacting the volume of ice they export, or discharge, from the ice sheet. While annual estimates of ice-sheet-wide discharge have been previously derived, higher-resolution records are required to fully constrain the temporal response of these glaciers to various climatic and mechanical drivers that vary in sub-annual scales. Here we sample outlet glaciers wider than 1 km ( N =230 ) to derive the first continuous, ice-sheet-wide record of total ice sheet discharge for the 2000–2016 period, resolving a seasonal variability of 6 %. The amplitude of seasonality varies spatially across the ice sheet from 5 % in the southeastern region to 9 % in the northwest region. We analyze seasonal to annual variability in the discharge time series with respect to both modeled meltwater runoff, obtained from RACMO2.3p2, and glacier front position changes over the same period. We find that year-to-year changes in total ice sheet discharge are related to annual front changes ( r 2 =0.59 , <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3" display="inline" overflow="scroll" dspmath="mathml"><mrow><mi>p</mi><mo>=</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">4</mn></mrow></msup></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="44pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="ffcc76c21433832f54aa79d0cec7f6aa"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="tc-12-3813-2018-ie00001.svg" width="44pt" height="15pt" src="tc-12-3813-2018-ie00001.png"/></svg:svg> ) and that the annual magnitude of discharge is closely related to cumulative front position changes ( r 2 =0.79 ), which show a net retreat of >400 km, or an average retreat of >2 km, at each surveyed glacier. Neither maximum seasonal runoff or annual runoff totals are correlated to annual discharge, which suggests that larger annual quantities of runoff do not relate to increased annual discharge. Discharge and runoff, however, follow similar patterns of seasonal variability with near-coincident periods of acceleration and seasonal maxima. These results suggest that changes in glacier front position drive secular trends in discharge, whereas the impact of runoff is likely limited to the summer months when observed seasonal variations are substantially controlled by the timing of meltwater input. |
format |
Text |
author |
King, Michalea D. Howat, Ian M. Jeong, Seongsu Noh, Myoung J. Wouters, Bert Noël, Brice Broeke, Michiel R. |
spellingShingle |
King, Michalea D. Howat, Ian M. Jeong, Seongsu Noh, Myoung J. Wouters, Bert Noël, Brice Broeke, Michiel R. Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
author_facet |
King, Michalea D. Howat, Ian M. Jeong, Seongsu Noh, Myoung J. Wouters, Bert Noël, Brice Broeke, Michiel R. |
author_sort |
King, Michalea D. |
title |
Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
title_short |
Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
title_full |
Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
title_fullStr |
Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
title_full_unstemmed |
Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet |
title_sort |
seasonal to decadal variability in ice discharge from the greenland ice sheet |
publishDate |
2018 |
url |
https://doi.org/10.5194/tc-12-3813-2018 https://tc.copernicus.org/articles/12/3813/2018/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
glacier Greenland Ice Sheet |
genre_facet |
glacier Greenland Ice Sheet |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-12-3813-2018 https://tc.copernicus.org/articles/12/3813/2018/ |
op_doi |
https://doi.org/10.5194/tc-12-3813-2018 |
container_title |
The Cryosphere |
container_volume |
12 |
container_issue |
12 |
container_start_page |
3813 |
op_container_end_page |
3825 |
_version_ |
1766009407714361344 |