Seasonal to decadal variability in ice discharge from the Greenland Ice Sheet

• Published in: The Cryosphere
• Main Authors: M. D. King, I. M. Howat, S. Jeong, M. J. Noh, B. Wouters, B. Noël, M. R. van den Broeke
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Greenland; glacier; Ice Sheet; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-12-3813-2018; https://doaj.org/article/e63b7bd88d3c4302828735e7e83091e1

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 ...