Influence of recent warming and ice dynamics on glacier surface elevations in the Canadian High Arctic, 1995–2014

ABSTRACTRepeat airborne laser altimetry measurements show widespread thinning (surface lowering) of glaciers in Canada's Queen Elizabeth Islands since 1995. Thinning rates averaged for 50 m elevation bins, were more than three times higher during the period 2005/06 to 2012/14 pentad than during the previous two pentads. Strongly negative thickness change (dh/dt) anomalies from 2005/06 to 2012/14, relative to the 1995–2012/14 mean, suggest that most of the measured thinning occurred during the most recent 5–6 year period when mean summer land surface temperatures (LSTs) were anomalously high and the mean summer black-sky shortwave broadband albedos (BSA) were anomalously low, relative to the 2000/01–15/16 period, and upper-air (700 hPa) and near surface (2 m) air temperatures were between 0.8°C and 1.5°C higher than 1995–2012 mean. Comparisons of dh/dt with mean summer LST and BSA measurements from the Moderate Resolution Imaging Spectroradiometer and with surface longitudinal strain rates computed from surface velocity fields derived from RADARSAT 1/2 and Landat-7 ETM + data suggest that surface elevation changes were driven mainly by changes in climate. An exception to this occurs along many fast-flowing outlet glaciers where ice dynamics appear also to have played an important role in surface elevation changes.

Download Full-text

Seasonal ice dynamics in the lower ablation zone of Dagongba Glacier, southeastern Tibetan Plateau, from multitemporal UAV images

Journal of Glaciology ◽

10.1017/jog.2021.123 ◽

2021 ◽

pp. 1-15

Author(s):

Yin Fu ◽

Qiao Liu ◽

Guoxiang Liu ◽

Bo Zhang ◽

Rui Zhang ◽

...

Keyword(s):

Tibetan Plateau ◽

Seasonal Dynamics ◽

Warm Season ◽

Cold Season ◽

Surface Elevation ◽

Surface Velocity ◽

Ablation Zone ◽

Glacier Surface ◽

Ice Dynamics ◽

Southeastern Tibetan Plateau

Abstract Most glaciers on the Tibetan Plateau have experienced continuous mass losses in response to global warming. However, the seasonal dynamics of glaciers on the southeastern Tibetan Plateau have rarely been reported in terms of glacier surface elevation and velocity. This paper presents a first attempt to explore the seasonal dynamics of the debris-covered Dagongba Glacier within the southeastern Tibetan Plateau. We use the multitemporal unoccupied aerial vehicle images collected over the lower ablation zone on 8 June and 17 October 2018, and 13 May 2019, and then perform an analysis concerning climatic fluctuations. The results reveal that the mean surface elevation decrease of the Dagongba Glacier during the warm season ( $2.81\pm 0.44$ m) was remarkably higher than the cold season ( $0.72\pm 0.45$ m). Particularly notable glacier surface elevation changes were found around supraglacial lakes and ice cliffs where ice ablation rates were $\sim$ 3 times higher than the average. In addition, a larger longitudinal decline of glacier surface velocity was observed in the warm season than that in the cold season. In terms of further comparative analysis, the Dagongba Glacier experienced a decrease in surface velocity between 1982–83 and 2018–19, with a decrease in the warm season possibly twice as large as that in the cold season.

Download Full-text

The Causes of Debris-Covered Glacier Thinning: Evidence for the Importance of Ice Dynamics From Kennicott Glacier, Alaska

Frontiers in Earth Science ◽

10.3389/feart.2021.680995 ◽

2021 ◽

Vol 9 ◽

Author(s):

Leif S. Anderson ◽

William H. Armstrong ◽

Robert S. Anderson ◽

Dirk Scherler ◽

Eric Petersen

Keyword(s):

Mass Balance ◽

Flow Direction ◽

Surface Velocity ◽

Glacier Surface ◽

Ice Dynamics ◽

Ice Flow ◽

Thickness Change ◽

Air Temperatures ◽

Compressive Flow ◽

Wide Range

The cause of debris-covered glacier thinning remains controversial. One hypothesis asserts that melt hotspots (ice cliffs, ponds, or thin debris) increase thinning, while the other posits that declining ice flow leads to dynamic thinning under thick debris. Alaska’s Kennicott Glacier is ideal for testing these hypotheses, as ice cliffs within the debris-covered tongue are abundant and surface velocities decline rapidly downglacier. To explore the cause of patterns in melt hotspots, ice flow, and thinning, we consider their evolution over several decades. We compile a wide range of ice dynamical and mass balance datasets which we cross-correlate and analyze in a step-by-step fashion. We show that an undulating bed that deepens upglacier controls ice flow in the lower 8.5 km of Kennicott Glacier. The imposed velocity pattern strongly affects debris thickness, which in turn leads to annual melt rates that decline towards the terminus. Ice cliff abundance correlates highly with the rate of surface compression, while pond occurrence is strongly negatively correlated with driving stress. A new positive feedback is identified between ice cliffs, streams and surface topography that leads to chaotic topography. As the glacier thinned between 1991 and 2015, surface melt in the study area decreased, despite generally rising air temperatures. Four additional feedbacks relating glacier thinning to melt changes are evident: the debris feedback (negative), the ice cliff feedback (negative), the pond feedback (positive), and the relief feedback (positive). The debris and ice cliff feedbacks, which are tied to the change in surface velocity in time, likely reduced melt rates in time. We show this using a new method to invert for debris thickness change and englacial debris content (∼0.017% by volume) while also revealing that declining speeds and compressive flow led to debris thickening. The expansion of debris on the glacier surface follows changes in flow direction. Ultimately, glacier thinning upvalley from the continuously debris-covered portion of Kennicott Glacier, caused by mass balance changes, led to the reduction of flow into the study area. This caused ice emergence rates to decline rapidly leading to the occurrence of maximum, glacier-wide thinning under thick, insulating debris.

Download Full-text

Surface elevation changes during 2007–13 on Bowdoin and Tugto Glaciers, northwestern Greenland

Journal of Glaciology ◽

10.1017/jog.2016.106 ◽

2016 ◽

Vol 62 (236) ◽

pp. 1083-1092 ◽

Cited By ~ 14

Author(s):

SHUN TSUTAKI ◽

SHIN SUGIYAMA ◽

DAIKI SAKAKIBARA ◽

TAKANOBU SAWAGAKI

Keyword(s):

Mass Balance ◽

Satellite Observations ◽

Surface Elevation ◽

Surface Mass Balance ◽

Elevation Change ◽

Predominant Role ◽

Ice Dynamics ◽

Surface Mass ◽

Elevation Changes ◽

Negative Surface

ABSTRACTTo quantify recent thinning of marine-terminating outlet glaciers in northwestern Greenland, we carried out field and satellite observations near the terminus of Bowdoin Glacier. These data were used to compute the change in surface elevation from 2007 to 2013 and this rate of thinning was then compared with that of the adjacent land-terminating Tugto Glacier. Comparing DEMs of 2007 and 2010 shows that Bowdoin Glacier is thinning more rapidly (4.1 ± 0.3 m a−1) than Tugto Glacier (2.8 ± 0.3 m a−1). The observed negative surface mass-balance accounts for <40% of the elevation change of Bowdoin Glacier, meaning that the thinning of Bowdoin Glacier cannot be attributable to surface melting alone. The ice speed of Bowdoin Glacier increases down-glacier, reaching 457 m a−1 near the calving front. This flow regime causes longitudinal stretching and vertical compression at a rate of −0.04 a−1. It is likely that this dynamically-controlled thinning has been enhanced by the acceleration of the glacier since 2000. Our measurements indicate that ice dynamics indeed play a predominant role in the rapid thinning of Bowdoin Glacier.

Download Full-text

Variations in the surface velocity of an alpine cirque glacier

Journal of Glaciology ◽

10.1017/jog.2018.85 ◽

2018 ◽

Vol 64 (248) ◽

pp. 969-976 ◽

Cited By ~ 1

Author(s):

J. W. SANDERS ◽

K. M. CUFFEY ◽

K. R. MACGREGOR ◽

J. L. KAVANAUGH ◽

C. F. DOW

Keyword(s):

Water System ◽

Heavy Rain ◽

Temporal Variations ◽

Surface Velocity ◽

Channel Network ◽

Glacier Surface ◽

Ice Dynamics ◽

Speed Up ◽

Water Volumes ◽

One Year

ABSTRACTFollowing pioneering work in Norway, cirque glaciers have widely been viewed as rigidly rotating bodies. This model is incorrect for basin-filling cirque glaciers, as we have demonstrated at West Washmawapta Glacier, a small glacier in the Canadian Rocky Mountains. Here we report observations at the same glacier that assess whether complex temporal variations of flow also occur. For parts of three summers, we measured daily displacements of the glacier surface. In one year, four short-duration speed-up events were recorded. Three of the events occurred during the intervals of warmest weather, when melt was most rapid; the fourth event occurred immediately following heavy rain. We interpret the speed-up events as manifestations of enhanced water inputs to the glacier bed and associated slip lubrication by increased water volumes and pressures. No further speed-ups occurred in the final month of the melt season, despite warm temperatures and several rainstorms; the dominant subglacial water system likely transformed from one of poorly connected cavities to one with an efficient channel network. The seasonal evolution of hydrology and flow resembles behaviors documented at other, larger temperate glaciers and indicates that analyses of cirque erosion cannot rely on simple assumptions about ice dynamics.

Download Full-text

Characterization of Canadian High Arctic glacier surface albedo from MODIS C6 data, 2001–2016

10.5194/tc-2017-160 ◽

2017 ◽

Author(s):

Colleen A. Mortimer ◽

Martin Sharp

Keyword(s):

Large Scale ◽

Surface Albedo ◽

Temporal Trends ◽

Principal Component ◽

High Arctic ◽

Shortwave Radiation ◽

Glacier Surface ◽

Annual Variations ◽

The Mean ◽

Moderate Resolution Imaging Spectroradiometer

Abstract. Inter-annual variations and longer-term trends in the annual mass balance of glaciers in Canada's Queen Elizabeth Islands (QEI) are largely attributable to changes in summer melt. The largest source of melt energy in the QEI in summer is net shortwave radiation, which is modulated by changes in glacier surface albedo. We used measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors to investigate large scale spatial patterns and temporal trends and variability in the summer surface albedo of QEI glaciers and their relationship to observed changes in glacier surface temperature from 2001 to 2016. Mean summer black-sky shortwave broadband albedo (BSA) decreased at a rate of 0.029 ± 0.025 decade-1 over that period. Larger reductions in BSA occurred in July (−0.050 ± 0.031 decade-1). No change in BSA was observed in either June or August. Most of the decrease in BSA, which was greatest at lower elevations around the margins of the ice masses, occurred between 2007 and 2012 when mean summer BSA was anomalously low. The First Principal Component of the 16-year record of mean summer BSA was well correlated with the mean summer North Atlantic Oscillation Index, except in 2006, 2010, and 2016. During this 16-year period, the mean summer LST increased by 0.046 ± 0.036 °C yr-1 and the BSA record was negatively correlated (−0.64, p

Download Full-text

Adjusting Two-Dimensional Velocity Data to Obey Continuity

Journal of Glaciology ◽

10.1017/s0022143000006341 ◽

1985 ◽

Vol 31 (108) ◽

pp. 115-119 ◽

Cited By ~ 2

Author(s):

L. A. Rasmussen

Keyword(s):

Stream Function ◽

Continuity Equation ◽

Sparse Matrix ◽

Linear Equations ◽

Surface Velocity ◽

Difference Approximation ◽

Central Difference ◽

Glacier Surface ◽

Thickness Change ◽

Solution Region

Abstract An algorithm is developed for adjusting glacier surface-velocity vectors, given on the nodes of a square grid, so that they obey a central-difference approximation of the continuity equation. Also required on the grid nodes are the glacier thickness, the ratio of the surface-velocity to the average velocity in the column, and the difference between the mass balance and the thickness change. All these other variables are assumed to be known exactly, and only the surface-velocity field is adjusted. The result is optimum in the sense that the magnitude of the adjustment is minimized. Either the relative or the absolute adjustment can be minimized, depending on how weights are specified. No restriction is placed on the shape of the solution region, and no boundary condition is required. The algorithm is not iterative. The algorithm first forms a parallel flow field that satisfies the continuity equation, and then uses a stream function to add a divergenceless field to it. The stream function that leads to the minimum velocity adjustment is obtained as four independent, interlacing solutions covering the solution region. For each of the four, a well-conditioned, sparse-matrix system of simultaneous linear equations is solved. A compact, sub-optimum, well-behaved iterative procedure is also developed for transforming part of the velocity adjustment into an adjustment of the thickness field.

Download Full-text

Glacier surface elevation changes in Rongbuk Catchment of the Central Himalayas in the last four decades

10.5194/egusphere-egu2020-9125 ◽

2020 ◽

Author(s):

Qinghua Ye ◽

Wei Nie ◽

Yimin Chen ◽

Gang Li ◽

lide Tian ◽

...

Keyword(s):

Climate Modeling ◽

Melting Rate ◽

Surface Elevation ◽

High Mountain ◽

Glacier Surface ◽

Important Indicator ◽

Central Himalayas ◽

Glacier Melting ◽

Elevation Changes ◽

Thinning Rate

Glaciers in the central Himalayas are important water resources for the downstream habitants, and accelerating melting of the high mountain glaciers speed up with continuous warming. We summerized the geodetic glacier surface elevation changes (Dh) by 6 data sets at different time periods during 1974-2016 in RongbukCatchment(RC) on the northern slope of Mt. Qomolangma (Mt. Everest) in the Central Himalayas. The result showed that glacier Dh varied with altitude and time, from -0.29 &#177; 0.03m a-1 in 1974-2000, to -0.47 &#177;0.24 m a-1 in 1974-2006,and -0.48 &#177;0.16 m a-1 in 1974-2012. Dh increased to -0.60 &#177; 0.20 m a-1 in 2000-2012, then decreased to-0.46 &#177; 0.24 m a-1 in 2000-2014, and by -0.49 &#177; 0.08 m a-1 in 2000-2016, showing a diverse rate being up - down- a little up. However, it generally presented a similar glacier thinning rate by -0.46~-0.49 m a-1 in the last four decades since 1970s in RC according to Dh1974-2006, Dh1974-2012, Dh2000-2014, and Dh2000-2016. Local meteorological observations revealed that, to a first order, the glacier thinning rate was kept the same pace with the number of annual melting days (MD). In spite of the obviously arising summer air temperature (TS) in 2000-2014, a slowdown glacier melting rate by -391 mm w.e.a-1 occurred in 2000-2014 because of less melting days with more precipitation and less annual mean temperature(Tm). It shows that MD is another important indicator and controlling factor to evaluate or to estimate glacier melting trend, especially in hydrological or climate modeling.

Download Full-text

Automatic mapping of land surface elevation changes from UAV-based imagery

International Journal of Remote Sensing ◽

10.1080/01431161.2016.1278313 ◽

2017 ◽

Vol 38 (8-10) ◽

pp. 2603-2622 ◽

Cited By ~ 15

Author(s):

Ivan Lizarazo ◽

Víctor Angulo ◽

Jorge Rodríguez

Keyword(s):

Land Surface ◽

Surface Elevation ◽

Elevation Changes ◽

Automatic Mapping

Download Full-text

Near-Surface and Land Surface Forecast System of the Vancouver 2010 Winter Olympic and Paralympic Games

Journal of Hydrometeorology ◽

10.1175/2011jhm1250.1 ◽

2011 ◽

Vol 12 (4) ◽

pp. 508-530 ◽

Cited By ~ 26

Author(s):

Natacha B. Bernier ◽

Stéphane Bélair ◽

Bernard Bilodeau ◽

Linying Tong

Keyword(s):

High Resolution ◽

Land Surface ◽

Snow Depth ◽

Land Surface Model ◽

Surface Model ◽

Near Surface ◽

Elevation Changes ◽

Forecast Models ◽

Operational Models ◽

Paralympic Games

Abstract A high-resolution 2D near-surface and land surface model was developed to produce snow and temperature forecasts over the complex alpine region of the Vancouver 2010 Winter Olympic and Paralympic Games. The model is driven by downscaled operational outputs from the Meteorological Service of Canada’s regional and global forecast models. Downscaling is applied to correct forcings for elevation differences between the operational forecast models and the high-resolution surface model. The high-resolution near-surface and land surface model is then used to further refine the forecasts. The model was validated against temperature and snow depth observations. The largest improvements were found in regions where low-resolution (i.e., on the order of 10 km or more) operational models typically lack the spatial resolution to capture rapid elevation changes. The model was found to better reproduce the intermittent snow cover at low-lying stations and to reduce snow depth error by as much as 3 m at alpine stations.

Download Full-text

High-resolution interactive modelling of the mountain glacier–atmosphere interface: an application over the Karakoram

The Cryosphere Discussions ◽

10.5194/tcd-7-103-2013 ◽

2013 ◽

Vol 7 (1) ◽

pp. 103-144 ◽

Cited By ~ 3

Author(s):

E. Collier ◽

T. Mölg ◽

F. Maussion ◽

D. Scherer ◽

C. Mayer ◽

...

Keyword(s):

High Resolution ◽

Mass Balance ◽

Land Surface ◽

Traditional Approach ◽

Coupled Model ◽

Glacier Mass Balance ◽

Glacier Surface ◽

Mountain Glacier ◽

Near Surface ◽

Basin Scale

Abstract. The traditional approach to simulations of alpine glacier mass balance (MB) has been one-way, or offline, thus precluding feedbacks from changing glacier surface conditions on the atmospheric forcing. In addition, alpine glaciers have been only simply, if at all, represented in atmospheric models to date. Here, we extend a recently presented, novel technique for simulating glacier–atmosphere interactions without the need for statistical downscaling, through the use of a coupled high-resolution mesoscale atmospheric and physically-based mass balance modelling system that includes glacier MB and energy balance feedbacks to the atmosphere. We compare the model results over the Karakoram region of the northwestern Himalaya with both remote sensing data and in situ glaciological and meteorological measurements for the ablation season of 2004. We find that interactive coupling has a localized but appreciable impact on the near-surface meteorological forcing data and that incorporation of MB processes improves the simulation of variables such as land surface temperature and snow albedo. Furthermore, including feedbacks from the MB model has a non-negligible effect on simulated mass balance, reducing modelled ablation, on average, by 0.1 m w.e. (−6.0%) to a total of −1.5 m w.e. between 25 June–31 August 2004. The interactively coupled model shows promise as a new, multi-scale tool for explicitly resolving atmospheric-MB processes of mountain glaciers at the basin scale.

Download Full-text