scholarly journals Spatio-temporal variations in seasonal ice tongue submarine melt rate at a tidewater glacier in southwest Greenland

2019 ◽  
Vol 65 (252) ◽  
pp. 523-530 ◽  
Author(s):  
A. N. MOYER ◽  
P. W. NIENOW ◽  
N. GOURMELEN ◽  
A. J. SOLE ◽  
D. A. SLATER ◽  
...  
Keyword(s):  
Dynamic System ◽  
Time Lapse ◽  
Temporal Variations ◽  
Flow Paths ◽  
Tidewater Glaciers ◽  
Grounding Line ◽  
Tidewater Glacier ◽  
Spatio Temporal ◽  
Southwest Greenland

ABSTRACTSubmarine melting of tidewater glaciers is proposed as a trigger for their recent thinning, acceleration and retreat. We estimate spring submarine melt rates (SMRs) of Kangiata Nunaata Sermia in southwest Greenland, from 2012 to 2014, by examining changes in along-fjord freeboard and velocity of the seasonal floating ice tongue. Estimated SMRs vary spatially and temporally near the grounding line, with mean rates of 1.3 ± 0.6, 0.8 ± 0.3 and 1.0 ± 0.4 m d−1across the tongue in 2012, 2013 and 2014, respectively. Higher melt rates correspond with locations of emerging subglacial plumes and terminus calving activity observed during the melt season using time-lapse camera imagery. Modelling of subglacial flow paths suggests a dynamic system capable of rapid re-routing of subglacial discharge both within and between melt seasons. Our results provide an empirically-derived link between the presence of subglacial discharge plumes and areas of high spring submarine melting and calving along glacier termini.

scholarly journals Spatially distributed runoff at the grounding line of a large Greenlandic tidewater glacier inferred from plume modelling

2017 ◽  
Vol 63 (238) ◽  
pp. 309-323 ◽  
Author(s):  
DONALD SLATER ◽  
PETER NIENOW ◽  
ANDREW SOLE ◽  
TOM COWTON ◽  
RUTH MOTTRAM ◽  
...  
Keyword(s):  
General Circulation ◽  
Circulation Model ◽  
Time Lapse ◽  
Atmospheric Temperature ◽  
Recent Change ◽  
Grounding Line ◽  
Tidewater Glacier ◽  
Spatially Distributed ◽  
Basal Sliding ◽  
Catchment Runoff

ABSTRACTUnderstanding the drivers of recent change at Greenlandic tidewater glaciers is of great importance if we are to predict how these glaciers will respond to climatic warming. A poorly constrained component of tidewater glacier processes is the near-terminus subglacial hydrology. Here we present a novel method for constraining near-terminus subglacial hydrology with application to marine-terminating Kangiata Nunata Sermia in South-west Greenland. By simulating proglacial plume dynamics using buoyant plume theory and a general circulation model, we assess the critical subglacial discharge, if delivered through a single compact channel, required to generate a plume that reaches the fjord surface. We then compare catchment runoff to a time series of plume visibility acquired from a time-lapse camera. We identify extended periods throughout the 2009 melt season where catchment runoff significantly exceeds the discharge required for a plume to reach the fjord surface, yet we observe no plume. We attribute these observations to spatial spreading of runoff across the grounding line. Persistent distributed drainage near the terminus would lead to more spatially homogeneous submarine melting and may promote more rapid basal sliding during warmer summers, potentially providing a mechanism independent of ocean forcing for increases in atmospheric temperature to drive tidewater glacier acceleration.

scholarly journals Influence of glacier runoff and near-terminus subglacial hydrology on frontal ablation at a large Greenlandic tidewater glacier

2020 ◽  
pp. 1-10
Author(s):  
Charlie Bunce ◽  
Peter Nienow ◽  
Andrew Sole ◽  
Tom Cowton ◽  
Benjamin Davison
Keyword(s):  
High Frequency ◽  
Greenland Ice Sheet ◽  
Time Lapse ◽  
Temporal Variations ◽  
Hydraulic Efficiency ◽  
Tidewater Glaciers ◽  
Total Mass Loss ◽  
Glacier Runoff ◽  
Iceberg Calving ◽  
Frontal Ablation

Abstract Frontal ablation from tidewater glaciers is a major component of the total mass loss from the Greenland ice sheet. It remains unclear, however, how changes in atmospheric and oceanic temperatures translate into changes in frontal ablation, in part due to sparse observations at sufficiently high spatial and temporal resolution. We present high-frequency time-lapse imagery (photos every 30 min) of iceberg calving and meltwater plumes at Kangiata Nunaata Sermia (KNS), southwest Greenland, during June–October 2017, alongside satellite-derived ice velocities and modelled subglacial discharge. Early in the melt season, we infer a subglacial hydrological network with multiple outlets that would theoretically distribute discharge and enhance undercutting by submarine melt, an inference supported by our observations of terminus-wide calving during this period. During the melt season, we infer hydraulic evolution to a relatively more channelised subglacial drainage configuration, based on meltwater plume visibility indicating focused emergence of subglacial water; these observations coincide with a reduction in terminus-wide calving and transition to an incised planform terminus geometry. We suggest that temporal variations in subglacial discharge and near-terminus subglacial hydraulic efficiency exert considerable influence on calving and frontal ablation at KNS.

scholarly journals Terminus-driven retreat of a major southwest Greenland tidewater glacier during the early 19th century: insights from glacier reconstructions and numerical modelling

2014 ◽  
Vol 60 (220) ◽  
pp. 333-344 ◽  
Author(s):  
James M. Lea ◽  
Douglas W.F. Mair ◽  
Faezeh M. Nick ◽  
Brice R. Rea ◽  
Anker Weidick ◽  
...  
Keyword(s):  
Relative Sensitivity ◽  
Ice Age ◽  
Early 19Th Century ◽  
Surface Mass ◽  
Tidewater Glaciers ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Historical Accounts ◽  
Instrumental Records ◽  
Southwest Greenland

AbstractTidewater glaciers in Greenland experienced widespread retreat during the last century. Information on their behaviour prior to this is often poorly constrained due to lack of observations, while determining the drivers prior to instrumental records is also problematic. Here we present a record of the dynamics of Kangiata Nunaata Sermia (KNS), southwest Greenland, from its Little Ice Age maximum (LIAmax) to 1859 – the period before continuous air temperature observations began at Nuuk in 1866. Using glacial geomorphology, historical accounts, photographs and GIS analyses, we provide evidence KNS was at its LIAmax by 1761, had retreated by ~5 km by 1808 and a further 7 km by 1859. This predates retreat at Jakobshavn Isbræ by 43–113 years, demonstrating the asynchroneity of tidewater glacier terminus response following the LIA. We use a one-dimensional flowband model to determine the relative sensitivity of KNS to atmospheric and oceanic climate forcing. Results demonstrate that terminus forcing rather than surface mass balance drove the retreat. Modelled glacier sensitivity to submarine melt rates is also insufficient to explain the retreat observed. However, moderate increases in crevasse water depth, driving an increase in calving, are capable of causing terminus retreat of the observed magnitude and timing.

Spatio-temporal variations of winter wheat water requirement and climatic causes in Huang-Huai-Hai Farming Region

2012 ◽  
Vol 20 (3) ◽  
pp. 356-362 ◽  
Author(s):  
Xiao-Lin YANG ◽  
Zhen-Wei SONG ◽  
Hong WANG ◽  
Quan-Hong SHI ◽  
Fu CHEN ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Temporal Variations ◽  
Water Requirement ◽  
Spatio Temporal

ASSESSMENT OF THE SPATIO-TEMPORAL VARIATIONS IN GROUND WATER STORAGE USING DOWN-SCALED GRACE DATA

2018 ◽  
Author(s):  
Hossein Sahour ◽  
◽  
Mohamed Sultan ◽  
Karem Abdelmohsen ◽  
Sita Karki ◽  
...  
Keyword(s):  
Ground Water ◽  
Water Storage ◽  
Temporal Variations ◽  
Grace Data ◽  
Spatio Temporal
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