Both social and engineering factors must be further explored and scrutinized across the globe—as should notions of justice related to flooding impacts and responses.
Image courtesy of Shutterstock.com/Ekaterina Pokrovsky.
New Research In
Physical Sciences
Featured Portals
Articles by Topic
Biological Sciences
Featured Portals
Articles by Topic
Edited by John H. England, University of Alberta, Edmonton, Canada, and accepted by the Editorial Board November 13, 2014 (received for review July 10, 2014)
Significance
Meltwater runoff from the Greenland ice sheet is a key contributor to global sea level rise and is expected to increase in the future, but it has received little observational study. We used satellite and in situ technologies to assess surface drainage conditions on the southwestern ablation surface after an extreme 2012 melting event. We conclude that the ice sheet surface is efficiently drained under optimal conditions, that digital elevation models alone cannot fully describe supraglacial drainage and its connection to subglacial systems, and that predicting outflow from climate models alone, without recognition of subglacial processes, may overestimate true meltwater release from the ice sheet.
Abstract
Thermally incised meltwater channels that flow each summer across melt-prone surfaces of the Greenland ice sheet have received little direct study. We use high-resolution WorldView-1/2 satellite mapping and in situ measurements to characterize supraglacial water storage, drainage pattern, and discharge across 6,812 km2 of southwest Greenland in July 2012, after a record melt event. Efficient surface drainage was routed through 523 high-order stream/river channel networks, all of which terminated in moulins before reaching the ice edge. Low surface water storage (3.6 ± 0.9 cm), negligible impoundment by supraglacial lakes or topographic depressions, and high discharge to moulins (2.54–2.81 cm⋅d−1) indicate that the surface drainage system conveyed its own storage volume every <2 d to the bed. Moulin discharges mapped inside ∼52% of the source ice watershed for Isortoq, a major proglacial river, totaled ∼41–98% of observed proglacial discharge, highlighting the importance of supraglacial river drainage to true outflow from the ice edge. However, Isortoq discharges tended lower than runoff simulations from the Modèle Atmosphérique Régional (MAR) regional climate model (0.056–0.112 km3⋅d−1 vs. ∼0.103 km3⋅d−1), and when integrated over the melt season, totaled just 37–75% of MAR, suggesting nontrivial subglacial water storage even in this melt-prone region of the ice sheet. We conclude that (i) the interior surface of the ice sheet can be efficiently drained under optimal conditions, (ii) that digital elevation models alone cannot fully describe supraglacial drainage and its connection to subglacial systems, and (iii) that predicting outflow from climate models alone, without recognition of subglacial processes, may overestimate true meltwater export from the ice sheet to the ocean.
Footnotes
- ↵1To whom correspondence should be addressed. Email: lsmith{at}geog.ucla.edu.
↵2Deceased January 9, 2015.
Author contributions: L.C.S. conceived the project; L.C.S., V.W.C., K.Y., C.J.G., L.H.P., A.K.R., C.J.L., and Y.S. designed research; A.E.B., A.L.L., D.C.F., and J.B. designed instrumentation; L.C.S., V.W.C., K.Y., C.J.G., L.H.P., A.K.R., C.J.L., A.E.B., B.T.O., S.E.M., M.T., R.R.F., A.L.L., and D.C.F. performed field work; V.W.C., K.Y., C.J.G., and L.H.P. conducted analyses; L.C.S. wrote the paper; and V.W.C., K.Y., C.J.G., and L.H.P. helped write the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission. J.H.E. is a guest editor invited by the Editorial Board.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1413024112/-/DCSupplemental.
Freely available online through the PNAS open access option.
Efficient melt drainage on the Greenland ice sheet
More Articles of This Classification
Physical Sciences
Related Content
Cited by...
Similar Articles
You May Also be Interested in
Blair Hedges discusses the state of Haiti's remaining forests and the consequences to biodiversity.
A study uncovers genetic evidence of early colonization of Jamaica by primates and suggests that adaptation can shape species morphology in novel environments, even when species come from morphologically conservative families.
Image courtesy of Lorraine Meeker (American Museum of Natural History, New York).
Researchers report that some moth species use sound absorbing-scales to avoid detection by bats and suggest that the findings could aid the design of biologically inspired sound absorbers for an array of applications, including noise mitigation and building acoustics.
Image courtesy of Thomas R. Neil.
Using phylogenetic analysis, researchers report that ants used plants for food and nesting long before plants evolved structures to accommodate arthropods, and although interactions with ants likely facilitated plant diversification, plant interactions did not shape ant diversification.
Image courtesy of Pixabay/cmolens.
