scholarly journals The retreat of a tidewater glacier: observations and model calculations on Hansbreen, Spitsbergen

2002 ◽  
Vol 48 (163) ◽  
pp. 592-600 ◽  
Author(s):  
Andreas Vieli ◽  
Jacek Jania ◽  
Lezek Kolondra
Keyword(s):  
Direct Response ◽  
Critical Height ◽  
Time Step ◽  
Model Calculations ◽  
Tidewater Glaciers ◽  
Water Line ◽  
Glacier Terminus ◽  
Front Position ◽  
Tidewater Glacier ◽  
Calving Rate

AbstractBased on observations and model calculations, the retreat over the last two decades of Hansbreen, a tidewater glacier in southern Spitsbergen, Svalbard, is investigated. The observations of the calving-front position between 1982 and 1998 show an abrupt retreat in 1990, which is suggested to be related to a depression in the glacier bed. The observed seasonal variations of the front position are mainly due to variations of the calving rate. The observations of Hansbreen further indicate that during periods of slow front-position changes, melting at the water-line may play an important role in triggering the process of calving. The evolution of Hansbreen between 1982 and 1998 is simulated with a numerical model for the dynamics of tidewater glaciers. Using a flotation criterion for calving in which for each time-step the part of the glacier terminus which is below a critical height above buoyancy is removed, we are able to reproduce the observed rapid retreat of Hansbreen through the depression in the glacier bed. From the observations and model calculations, we conclude that the rapid retreat is mainly an effect of basal topography in the terminus region and not a direct response to a change in mass balance.

Dynamics of tidewater glaciers: comparison of three models

2006 ◽  
Vol 52 (177) ◽  
pp. 183-190 ◽  
Author(s):  
F.M. Nick ◽  
J. Oerlemans
Keyword(s):  
Water Depth ◽  
Mass Conservation ◽  
Equilibrium States ◽  
The Other ◽  
Tidewater Glaciers ◽  
One Dimensional ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Linear Behaviour ◽  
Calving Rate

AbstractA minimal model of a tidewater glacier based solely on mass conservation is compared with two one-dimensional numerical flowline models, one with the calving rate proportional to water depth, and the other with the flotation criterion as a boundary condition at the glacier terminus. The models were run with two simplified bed geometries and two mass-balance formulations. The models simulate the full cycle of length variations and the equilibrium states for a tidewater glacier. This study shows that the branching of the equilibrium states depends significantly on the bed geometry. The similarity between the results of the three models indicates that if there is a submarine undulation at the terminus of a tidewater glacier, any model in which the frontal ice loss is related to the water depth yields qualitatively the same non-linear behaviour. For large glaciers extending into deep water, the flotation model causes unrealistic behaviour.

scholarly journals Tidewater calving

1996 ◽  
Vol 42 (141) ◽  
pp. 375-385 ◽  
Author(s):  
С.J. Van Der Veen
Keyword(s):  
Water Depth ◽  
Fold Increase ◽  
Actual Rate ◽  
Tidewater Glaciers ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Iceberg Calving ◽  
Speed Up ◽  
Calving Rate ◽  
Subglacial Drainage

AbstractData from Columbia Glacier are used to identify processes that control calving from a temperate tidewater glacier and to re-evaluate models that have been proposed to describe iceberg calving. Since 1981, Columbia Glacier has been retreating rapidly, with an almost seven-fold increase in calving rate from the mid-1970s to 1993. At the same time, the speed of the glacier increased almost as much, so that the actual rate of retreat increased more slowly. According to the commonly accepted model, the calving rate is linearly related to the water depth at the terminus, with retreat of the glacier snout into deeper water, leading to larger calving rates and accelerated retreat. The Columbia Glacier data show that the calving rate is not simply linked to observed quantities such as water depth or stretching rate near the terminus. During the retreat, the thickness at the terminus appears to be linearly correlated with the water depth; at the terminus, the thickness in excess of flotation remained at about 50 m. This suggests that retreat may be initiated when the terminal thickness becomes too small, with the rate of retreat controlled by the rate at which the snout is thinning and by the basal slope. The implication is that the rapid retreat of Columbia Glacier (and other comparable tidewater glaciers) is not the result of an increase in calving as the glacier retreated into deeper water. Instead, the retreat was initiated and maintained by thinning of the glacier. For Columbia Glacier, the continued thinning is probably associated with the increase in glacier speed and retreat may be expected to continue as long as these large speeds are maintained. It is not clear what mechanism may be responsible for the speed-up but the most likely candidate is a change in basal conditions or subglacial drainage. Consequently, the behavior of tidewater glaciers may be controlled by processes acting at the glacier bed rather than by what happens at the glacier terminus.

scholarly journals Tidewater calving

1996 ◽  
Vol 42 (141) ◽  
pp. 375-385 ◽  
Author(s):  
С.J. Van Der Veen
Keyword(s):  
Water Depth ◽  
Fold Increase ◽  
Actual Rate ◽  
Tidewater Glaciers ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Iceberg Calving ◽  
Speed Up ◽  
Calving Rate ◽  
Subglacial Drainage

AbstractData from Columbia Glacier are used to identify processes that control calving from a temperate tidewater glacier and to re-evaluate models that have been proposed to describe iceberg calving. Since 1981, Columbia Glacier has been retreating rapidly, with an almost seven-fold increase in calving rate from the mid-1970s to 1993. At the same time, the speed of the glacier increased almost as much, so that the actual rate of retreat increased more slowly. According to the commonly accepted model, the calving rate is linearly related to the water depth at the terminus, with retreat of the glacier snout into deeper water, leading to larger calving rates and accelerated retreat. The Columbia Glacier data show that the calving rate is not simply linked to observed quantities such as water depth or stretching rate near the terminus. During the retreat, the thickness at the terminus appears to be linearly correlated with the water depth; at the terminus, the thickness in excess of flotation remained at about 50 m. This suggests that retreat may be initiated when the terminal thickness becomes too small, with the rate of retreat controlled by the rate at which the snout is thinning and by the basal slope. The implication is that the rapid retreat of Columbia Glacier (and other comparable tidewater glaciers) is not the result of an increase in calving as the glacier retreated into deeper water. Instead, the retreat was initiated and maintained by thinning of the glacier. For Columbia Glacier, the continued thinning is probably associated with the increase in glacier speed and retreat may be expected to continue as long as these large speeds are maintained. It is not clear what mechanism may be responsible for the speed-up but the most likely candidate is a change in basal conditions or subglacial drainage. Consequently, the behavior of tidewater glaciers may be controlled by processes acting at the glacier bed rather than by what happens at the glacier terminus.

scholarly journals Relationship between tidewater glacier calving velocity and water depth at the calving front

1991 ◽  
Vol 15 ◽  
pp. 115-118 ◽  
Author(s):  
Mauri S. Pelto ◽  
Charles R. Warren
Keyword(s):  
Water Depth ◽  
Reasonable Accuracy ◽  
Ice Streams ◽  
Ice Shelves ◽  
Tidewater Glaciers ◽  
Tidewater Glacier ◽  
Iceberg Calving ◽  
Calving Rate ◽  
The Relationship ◽  
Water Depths

An analysis of the relationship between iceberg calving rates and water depth has been completed for 22 tidewater glaciers. A linear relationship provides reasonable accuracy, with a correlation coefficient of 0.85, for all tidewater glaciers examined, whether they be polar or temperate. The polar glaciers have a slightly lower calving rate for a given water depth. This relationship indicates a lower calving rate for water depths over 50 m than determined by Brown and others (1982). It is based only on glaciers or ice streams and cannot be applied to ice shelves.

scholarly journals Relationship between tidewater glacier calving velocity and water depth at the calving front

1991 ◽  
Vol 15 ◽  
pp. 115-118 ◽  
Author(s):  
Mauri S. Pelto ◽  
Charles R. Warren
Keyword(s):  
Water Depth ◽  
Reasonable Accuracy ◽  
Ice Streams ◽  
Ice Shelves ◽  
Tidewater Glaciers ◽  
Tidewater Glacier ◽  
Iceberg Calving ◽  
Calving Rate ◽  
The Relationship ◽  
Water Depths

An analysis of the relationship between iceberg calving rates and water depth has been completed for 22 tidewater glaciers. A linear relationship provides reasonable accuracy, with a correlation coefficient of 0.85, for all tidewater glaciers examined, whether they be polar or temperate. The polar glaciers have a slightly lower calving rate for a given water depth. This relationship indicates a lower calving rate for water depths over 50 m than determined by Brown and others (1982). It is based only on glaciers or ice streams and cannot be applied to ice shelves.

scholarly journals A minimal model of a tidewater glacier

2005 ◽  
Vol 42 ◽  
pp. 1-6 ◽  
Author(s):  
J. Oerlemans ◽  
F.M. Nick
Keyword(s):  
Velocity Field ◽  
Water Depth ◽  
Ice Thickness ◽  
Global Dynamics ◽  
Equilibrium Line Altitude ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Glacier Length ◽  
Parameterized Model ◽  
Calving Rate

AbstractWe propose a simple, highly parameterized model of a tidewater glacier. The mean ice thickness and the ice thickness at the glacier front are parameterized in terms of glacier length and, when the glacier is calving, water depth. We use a linear relation between calving rate and water depth. The change in glacier length is determined by the total change in the mass budget (surface balance and calving flux), but not by the details of the glacier profile and the related velocity field. We show that this may still yield relatively rapid rates of retreat for an idealized bed geometry with a smooth overdeepening. The model is able to simulate the full cycle of ice-free conditions, glacier terminus on land, tidewater glaciers terminus, and backwards. We study two cases: (i) a glacier with a specific balance (accumulation) that is spatially uniform, and (ii) a glacier in a warmer climate with the specific balance being a linear function of altitude. Equilibrium states exhibit a double branching with respect to the climatic forcing (equilibrium-line altitude). One bifurcation is related to the dependence of the calving process on the bed profile; the other bifurcation is due to the height–mass-balance feedback. We discuss the structure of the solution diagram for different values of the calving-rate parameter. The model results are similar to those of Vieli and others (2001), who combined a fairly sophisticated two-dimensional (vertical plane) numerical ice-flow model with the modified flotation criterion suggested by Van der Veen (1996). With regard to the global dynamics of a tidewater glacier, we conclude that the details of the glacier profile or velocity field are less significant than the bed profile and the relation between the water depth and the calving rate.

scholarly journals Estimating Greenland tidewater glacier retreat driven by submarine melting

2019 ◽  
Vol 13 (9) ◽  
pp. 2489-2509 ◽  
Author(s):  
Donald A. Slater ◽  
Fiamma Straneo ◽  
Denis Felikson ◽  
Christopher M. Little ◽  
Heiko Goelzer ◽  
...  
Keyword(s):  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacier Retreat ◽  
Ocean Temperature ◽  
Position Change ◽  
Tidewater Glaciers ◽  
The North ◽  
Glacier Terminus ◽  
Tidewater Glacier

Abstract. The effect of the North Atlantic Ocean on the Greenland Ice Sheet through submarine melting of Greenland's tidewater glacier calving fronts is thought to be a key driver of widespread glacier retreat, dynamic mass loss and sea level contribution from the ice sheet. Despite its critical importance, problems of process complexity and scale hinder efforts to represent the influence of submarine melting in ice-sheet-scale models. Here we propose parameterizing tidewater glacier terminus position as a simple linear function of submarine melting, with submarine melting in turn estimated as a function of subglacial discharge and ocean temperature. The relationship is tested, calibrated and validated using datasets of terminus position, subglacial discharge and ocean temperature covering the full ice sheet and surrounding ocean from the period 1960–2018. We demonstrate a statistically significant link between multi-decadal tidewater glacier terminus position change and submarine melting and show that the proposed parameterization has predictive power when considering a population of glaciers. An illustrative 21st century projection is considered, suggesting that tidewater glaciers in Greenland will undergo little further retreat in a low-emission RCP2.6 scenario. In contrast, a high-emission RCP8.5 scenario results in a median retreat of 4.2 km, with a quarter of tidewater glaciers experiencing retreat exceeding 10 km. Our study provides a long-term and ice-sheet-wide assessment of the sensitivity of tidewater glaciers to submarine melting and proposes a practical and empirically validated means of incorporating ocean forcing into models of the Greenland ice sheet.

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.

scholarly journals Past and future response of Greenland's tidewater glaciers to submarine melting

2019 ◽  
Author(s):  
Donald Slater ◽  
Fiamma Straneo ◽  
Denis Felikson ◽  
Chris Little ◽  
Heiko Goelzer ◽  
...  
Keyword(s):  
North Atlantic Ocean ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ocean Temperature ◽  
Tidewater Glaciers ◽  
The North ◽  
Glacier Terminus ◽  
Scale Models ◽  
Tidewater Glacier ◽  
Process Complexity

Abstract. The effect of the North Atlantic Ocean on the Greenland Ice Sheet through submarine melting of Greenland's tidewater glacier calving fronts is thought to be a key driver of widespread glacier retreat, dynamic mass loss and sea level contribution from the ice sheet. Despite its critical importance, problems of process complexity and scale hinder efforts to represent the influence of submarine melting in ice sheet-scale models. Here we propose parameterizing tidewater glacier terminus position as a simple linear function of submarine melting, with submarine melting in turn estimated as a function of subglacial runoff and ocean temperature. The relationship is tested, calibrated and validated using datasets of terminus position, runoff and ocean temperature covering the full ice sheet and surrounding ocean from the period 1960–present. We demonstrate a statistically significant link between multi-decadal tidewater glacier terminus position and submarine melting and show that the proposed parameterisation has predictive power when considering a population of glaciers. An illustrative 21st century projection is considered suggesting that tidewater glaciers in Greenland will undergo little further retreat in a low emissions RCP2.6 scenario. In contrast, a high emissions RCP8.5 scenario results in a median retreat of ∼6 km, with 35 % of glaciers experiencing retreat exceeding 10 km. Our study provides a long-term and ice sheet-wide assessment of the sensitivity of tidewater glaciers to submarine melting and proposes a practical and empirically validated means of incorporating ocean forcing into models of the Greenland ice sheet.

scholarly journals Processes and patterns of glacier-influenced sedimentation and recent tidewater glacier dynamics in Darbel Bay, western Antarctic Peninsula

2019 ◽  
Vol 31 (4) ◽  
pp. 218-227 ◽  
Author(s):  
C.L. Batchelor ◽  
J.A. Dowdeswell ◽  
K.A. Hogan ◽  
R.D. Larter ◽  
E. Parsons ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Decadal Variability ◽  
Western Antarctic Peninsula ◽  
Ice Dynamics ◽  
Tidewater Glaciers ◽  
Bathymetric Data ◽  
Glacier Terminus ◽  
Tidewater Glacier ◽  
Landsat Satellite ◽  
Glacial Landforms

AbstractBathymetric data of unprecedented resolution are used to provide insights into former ice dynamics and glacial processes in a western Antarctic Peninsula embayment. An assemblage of submarine glacial landforms, which includes subglacially produced streamlined features and ice-marginal ridges, reveals the former pattern of ice flow and retreat. A group of more than 250 small (< 1–3 m high, 10–20 m wide) and relatively evenly spaced recessional moraines was identified beyond the margin of Philippa Glacier. The small recessional moraines are interpreted to have been produced during short-lived, possibly annual re-advances of a grounded ice margin during overall retreat. This is the first time that these features have been shown to be part of the assemblage of landforms produced by tidewater glaciers on the Antarctic Peninsula. Glacier-terminus changes during the last four decades, mapped from LANDSAT satellite images, were analysed to determine whether the moraines were produced during recent still-stands or re-advances of Philippa Glacier and to further investigate the short-term (annual to decadal) variability in ice-marginal position in tidewater glacier systems. The asynchronous response of individual tidewater glaciers in Darbel Bay is interpreted to be controlled mainly by local topography rather than by glacier catchment-area size.

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