Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet
<p>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...
| 出版年: | The Cryosphere |
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| 主要な著者: | , , , , , , |
| フォーマット: | 論文 |
| 言語: | 英語 |
| 出版事項: |
Copernicus Publications
2018-12-01
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| 主題: | |
| オンライン･アクセス: | https://www.the-cryosphere.net/12/3813/2018/tc-12-3813-2018.pdf |
| 要約: | <p>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
(<span class="inline-formula"><i>N</i>=230</span>) 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 (<span class="inline-formula"><i>r</i><sup>2</sup>=0.59</span>, <span class="inline-formula"><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><span><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></span></span>) and that the annual
magnitude of discharge is closely related to cumulative front position
changes (<span class="inline-formula"><i>r</i><sup>2</sup>=0.79</span>), which show a net retreat of <span class="inline-formula">>400</span> km,
or an average retreat of <span class="inline-formula">>2</span> 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.</p> |
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| ISSN: | 1994-0416 1994-0424 |