Southwest Greenland ice-sheet retreat during the 8.2 ka cold event

2021 ◽  
Vol 268 ◽  
pp. 107101
Author(s):  
Anders E. Carlson ◽  
Alberto V. Reyes ◽  
Kaja Sillett ◽  
Klaus M. Wilcken ◽  
Dylan H. Rood
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Cold Event ◽  
Southwest Greenland

scholarly journals Impact of freshwater runoff from the southwest Greenland Ice Sheet on fjord productivity since the late 19th century

2022 ◽  
Author(s):  
Mimmi Oksman ◽  
Anna Bang Kvorning ◽  
Signe Hillerup Larsen ◽  
Kristian Kjellerup Kjeldsen ◽  
Kenneth David Mankoff ◽  
...  
Keyword(s):  
19Th Century ◽  
Biogenic Silica ◽  
Temporal Trends ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Coastal Ecosystems ◽  
Late 19Th Century ◽  
Temporal Perspective ◽  
Freshwater Runoff ◽  
Southwest Greenland

Abstract. Climate warming and the resulting acceleration of freshwater discharge from the Greenland Ice Sheet are impacting Arctic marine coastal ecosystems, with implications for their biological productivity. To accurately project the future of coastal ecosystems, and place recent trends into perspective, paleo-records are essential. Here, we present late 19th century to present runoff estimates for a large sub-Arctic fjord system (Nuup Kangerlua, southwest Greenland) influenced by both marine- and land-terminating glaciers. We followed a multiproxy approach to reconstruct spatial and temporal trends in primary production from four sediment cores, including diatom fluxes and assemblage composition changes, biogeochemical and sedimentological proxies (total organic carbon, nitrogen, C / N-ratio, biogenic silica, δ13C, δ15N, grain size distribution). We show that an abrupt increase in freshwater runoff in the mid-1990’s is reflected by a 3-fold increase in biogenic silica fluxes in the glacier-proximal area of the fjord. In addition to increased productivity, freshwater runoff modulates the diatom assemblages and drives the dynamics and magnitude of the diatom spring bloom. Our records indicate that marine productivity is higher today than it has been at any point since the late 19th century and suggest that increased mass loss of the Greenland Ice Sheet is likely to continue promoting high productivity levels at sites proximal to marine-terminating glaciers. We highlight the importance of paleo-records in offering a unique temporal perspective on ice-ocean-ecosystem responses to climate forcing beyond existing remote sensing or monitoring time-series.

scholarly journals Maximum Southwest Greenland Ice Sheet Recession in the Early Holocene

2020 ◽  
Vol 47 (1) ◽  
Author(s):  
A. J. Lesnek ◽  
J. P. Briner ◽  
N. E. Young ◽  
J. K. Cuzzone
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Early Holocene ◽  
Southwest Greenland

scholarly journals Efficient meltwater drainage through supraglacial streams and rivers on the southwest Greenland ice sheet

2015 ◽  
Vol 112 (4) ◽  
pp. 1001-1006 ◽  
Author(s):  
Laurence C. Smith ◽  
Vena W. Chu ◽  
Kang Yang ◽  
Colin J. Gleason ◽  
Lincoln H. Pitcher ◽  
...  
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Water Storage ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Drainage Pattern ◽  
Order Stream ◽  
Surface Drainage ◽  
Ice Edge ◽  
Southwest Greenland

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.

scholarly journals Cosmogenic isotope measurements from recently deglaciated bedrock as a new tool to decipher changes in Greenland Ice Sheet size

2020 ◽  
Author(s):  
Nicolás E. Young ◽  
Alia J. Lesnek ◽  
Josh K. Cuzzone ◽  
Jason P. Briner ◽  
Jessica A. Badgeley ◽  
...  
Keyword(s):  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Model Data ◽  
Climate History ◽  
Surface Mass ◽  
Current Configuration ◽  
Maximum Extent ◽  
Geologic Record ◽  
Southwest Greenland

Abstract. During the middle to late Holocene (8.2 ka BP to present), the Greenland Ice Sheet (GrIS) was smaller than its current configuration. Determining the exact dimensions of the Holocene ice-sheet minimum and the duration that the ice margin rested inboard of its current position remains challenging. Contemporary retreat of the GrIS from its historical maximum extent in southwestern Greenland is exposing a landscape that holds clues regarding the configuration and timing of past ice-sheet minima. To quantify the duration of the time the GrIS margin was near its modern extent we develop a new technique on Greenland that utilizes in situ cosmogenic 10Be-14C-26Al in bedrock samples that have become ice free only in the last few decades by the retreating ice-sheet margin at Kangiata Nunaata Sermia (n = 12 sites; KNS), southwest Greenland. To maximize the utility of this approach, we refine the deglaciation history of the region with stand-alone 10Be measurements (n = 49) and traditional 14C ages from sedimentary deposits contained in proglacial-threshold lakes. We combine our reconstructed ice-margin history in the KNS region with additional geologic records from southwestern Greenland and recent model simulations of GrIS change, to constrain the timing of the GrIS minimum in southwest Greenland, the magnitude of Holocene inland GrIS retreat, and explore the regional climate history influencing Holocene ice-sheet behavior. Our 10Be-14C-26Al measurements reveal that 1) KNS retreated behind its modern margin just before 10 ka, but likely stabilized near the present GrIS margin for several thousand years before retreating farther inland, and 2) pre-Holocene 10Be detected in several of our sample sites is most easily explained by several thousand years of surface exposure during the Last Interglaciation. Moreover, our new results indicate that the minimum extent of the GrIS likely occurred after ~ 5 ka, and the GrIS margin may have approached its eventual historical maximum extent as early as ~ 2 ka. Recent simulations of GrIS change are able to match the geologic record of ice-sheet change in regions dominated by surface mass balance, but produce a poorer model-data fit in areas influenced by oceanic and dynamic processes. Simulations that achieve the best model-data fit suggest that inland retreat of the ice margin driven by early to middle Holocene warmth may have been mitigated by increased precipitation. Triple 10Be-14C-26Al measurements in recently deglaciated bedrock provide a new tool to help decipher the duration of smaller-than-present ice over multiple timescales. Modern retreat of the GrIS margin in southwest Greenland is revealing a bedrock landscape that was also exposed during the migration of the GrIS margin towards its Holocene minimum extent, but has yet to tap into a landscape that remained ice covered throughout the entire Holocene.

scholarly journals Near surface meltwater storage in low-density bare ice of the Greenland ice sheet ablation zone

2017 ◽  
Author(s):  
Matthew G. Cooper ◽  
Laurence C. Smith ◽  
Asa K. Rennermalm ◽  
Clément Miège ◽  
Lincoln H. Pitcher ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Low Density ◽  
Ablation Zone ◽  
Near Surface ◽  
Sheet Surface ◽  
Water Saturated ◽  
Southwest Greenland

Abstract. We document the density and hydrologic properties of bare, ablating ice in a mid-elevation (1215 m a.s.l.) supraglacial internally drained catchment near Kangerlussuaq, southwest Greenland. We find water saturated, low-density (474–725 kg m−3, μ = 688 kg m−3) ice to at least 1.1 m depth below the ice sheet surface. This near surface, low-density ice consists of alternating fractured porous ice and clear solid ice lenses, overlain by a thin (

scholarly journals Seasonal evolution of supraglacial lakes and rivers on the southwest Greenland Ice Sheet

2021 ◽  
pp. 1-11
Author(s):  
Kang Yang ◽  
Laurence C. Smith ◽  
Matthew G. Cooper ◽  
Lincoln H. Pitcher ◽  
Dirk van As ◽  
...  
Keyword(s):  
Surface Runoff ◽  
Climate Models ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Elevation ◽  
Landsat 8 ◽  
Seasonal Evolution ◽  
Supraglacial Lakes ◽  
Independent Features ◽  
Southwest Greenland

Abstract Supraglacial lakes and rivers dominate the storage and transport of meltwater on the southwest Greenland Ice Sheet (GrIS) surface. Despite functioning as interconnected hydrologic networks, supraglacial lakes and rivers are commonly studied as independent features, resulting in an incomplete understanding of their collective impact on meltwater storage and routing. We use Landsat 8 satellite imagery to assess the seasonal evolution of supraglacial lakes and rivers on the southwest GrIS during the 2015 melt season. Remotely sensed meltwater areas and volumes are compared with surface runoff simulations from three climate models (MERRA-2, MAR 3.6 and RACMO 2.3), and with in situ observations of proglacial discharge in the Watson River. We find: (1) at elevations >1600 m, 21% of supraglacial lakes and 28% of supraglacial rivers drain into moulins, signifying the presence of high-elevation surface-to-bed meltwater connections even during a colder-than-average melt season; (2) while supraglacial lakes dominate instantaneous surface meltwater storage, supraglacial rivers dominate total surface meltwater area and discharge; (3) the combined surface area of supraglacial lakes and rivers is strongly correlated with modeled surface runoff; and (4) of the three models examined here, MERRA-2 runoff yields the highest overall correlation with observed proglacial discharge in the Watson River.

scholarly journals In situ cosmogenic <sup>10</sup>Be–<sup>14</sup>C–<sup>26</sup>Al measurements from recently deglaciated bedrock as a new tool to decipher changes in Greenland Ice Sheet size

2021 ◽  
Vol 17 (1) ◽  
pp. 419-450
Author(s):  
Nicolás E. Young ◽  
Alia J. Lesnek ◽  
Josh K. Cuzzone ◽  
Jason P. Briner ◽  
Jessica A. Badgeley ◽  
...  
Keyword(s):  
Regional Climate ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Model Data ◽  
Climate History ◽  
Surface Mass ◽  
Current Configuration ◽  
Maximum Extent ◽  
Southwest Greenland

Abstract. Sometime during the middle to late Holocene (8.2 ka to ∼ 1850–1900 CE), the Greenland Ice Sheet (GrIS) was smaller than its current configuration. Determining the exact dimensions of the Holocene ice-sheet minimum and the duration that the ice margin rested inboard of its current position remains challenging. Contemporary retreat of the GrIS from its historical maximum extent in southwestern Greenland is exposing a landscape that holds clues regarding the configuration and timing of past ice-sheet minima. To quantify the duration of the time the GrIS margin was near its modern extent we develop a new technique for Greenland that utilizes in situ cosmogenic 10Be–14C–26Al in bedrock samples that have become ice-free only in the last few decades due to the retreating ice-sheet margin at Kangiata Nunaata Sermia (n=12 sites, 36 measurements; KNS), southwest Greenland. To maximize the utility of this approach, we refine the deglaciation history of the region with stand-alone 10Be measurements (n=49) and traditional 14C ages from sedimentary deposits contained in proglacial–threshold lakes. We combine our reconstructed ice-margin history in the KNS region with additional geologic records from southwestern Greenland and recent model simulations of GrIS change to constrain the timing of the GrIS minimum in southwest Greenland and the magnitude of Holocene inland GrIS retreat, as well as to explore the regional climate history influencing Holocene ice-sheet behavior. Our 10Be–14C–26Al measurements reveal that (1) KNS retreated behind its modern margin just before 10 ka, but it likely stabilized near the present GrIS margin for several thousand years before retreating farther inland, and (2) pre-Holocene 10Be detected in several of our sample sites is most easily explained by several thousand years of surface exposure during the last interglaciation. Moreover, our new results indicate that the minimum extent of the GrIS likely occurred after ∼5 ka, and the GrIS margin may have approached its eventual historical maximum extent as early as ∼2 ka. Recent simulations of GrIS change are able to match the geologic record of ice-sheet change in regions dominated by surface mass balance, but they produce a poorer model–data fit in areas influenced by oceanic and dynamic processes. Simulations that achieve the best model–data fit suggest that inland retreat of the ice margin driven by early to middle Holocene warmth may have been mitigated by increased precipitation. Triple 10Be–14C–26Al measurements in recently deglaciated bedrock provide a new tool to help decipher the duration of smaller-than-present ice over multiple timescales. Modern retreat of the GrIS margin in southwest Greenland is revealing a bedrock landscape that was also exposed during the migration of the GrIS margin towards its Holocene minimum extent, but it has yet to tap into a landscape that remained ice-covered throughout the entire Holocene.

Fluvial morphometry of supraglacial river networks on the southwest Greenland Ice Sheet

2016 ◽  
Vol 53 (4) ◽  
pp. 459-482 ◽  
Author(s):  
Kang Yang ◽  
Laurence C. Smith ◽  
Vena W. Chu ◽  
Lincoln H. Pitcher ◽  
Colin J. Gleason ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
River Networks ◽  
Southwest Greenland

The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change

1997 ◽  
pp. 95-103 ◽  
Author(s):  
Henrik Højmark Thomsen ◽  
Niels Reeh ◽  
Ole B. Olesen ◽  
Carl Egede Bøggilde ◽  
Wolfgang Starzer ◽  
...  
Keyword(s):  
Climatic Change ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
East Greenland ◽  
Changing Climate ◽  
North East ◽  
Integrated Research ◽  
Research Themes ◽  
Advance Research ◽  
Inland Ice

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Højmark Thomsen, H., Reeh, N., Olesen, O. B., Egede Bøggilde, C., Starzer, W., Weidick, A., & Higgins, A. K. (1997). The Nioghalvfjerdsfjorden glacier project, North-East Greenland: a study of ice sheet response to climatic change. Geology of Greenland Survey Bulletin, 176, 95-103. https://doi.org/10.34194/ggub.v176.5073 _______________ Glaciological research was initiated in 1996 on the floating glacier tongue filling Nioghalvfjerdsfjorden in NorthEast Greenland (Fig. 1), with the aim of acquiring a better understanding of the response of the Greenland ice sheet (Inland Ice) to changing climate, and the implications for future sea level. The research is part of a three year project (1996–98) to advance research into the basic processes that contribute to changes in the ocean volume with a changing climate. Five nations are participants in the project, which is supported by the European Community (EC) Environment and Climate Programme. The Geological Survey of Denmark and Greenland (GEUS) and the Danish Polar Center are the Danish partners in the project, both with integrated research themes concentrated on and around Nioghalvfjerdsfjorden.

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