How much can we benefit from the combination of numerical simulation and in situ observations? A case study on an Arctic polythermal valley glacier

Ice flow velocity is sensitive to glacier variations both controlling and representing the delivery of ice and affecting the future stability of ice masses in a warming climate. Austre Lov&#233;nbreen (AL) is one of the poly-thermal glaciers in the high Arctic and located on the northwestern coast of Spitsbergen, Svalbard. The ice flow velocity of AL was investigated using in situ global positioning system (GPS) observations over 15 years and numerical modelling with Elmer/Ice. First, the ice flow velocity field of AL along central flow line was presented. While AL moves slowly at a speed of approximate 4 m/a, obvious seasonal changes of ice flow velocity can be found in the middle of the glacier, where the velocity in spring-summer is 47% larger than in autumn&#8211;winter in 2016, and the mean annual velocity variation in different seasons is 14% from 2009 until 2016. Second, the numerical simulation was performed considering the poly-thermal character of the glacier, and indicated that there are two peak ice flow regions on the glacier, and not just one peak ice flow region as previously believed. The new peak ice flow zone found by simulation was verified by field work, which also demonstrated that the velocity of the newly identified zone is 8% faster than the previously identified zone. Third, although our field observations showed that the ice flow velocity is slowly increasing recently, the maximum ice flow velocity will soon begin to decrease gradually in the long term according to glacier evolution modelling of AL.

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Discovery of the Fastest Ice Flow along the Central Flow Line of Austre Lovénbreen, a Poly-thermal Valley Glacier in Svalbard

Remote Sensing ◽

10.3390/rs11121488 ◽

2019 ◽

Vol 11 (12) ◽

pp. 1488 ◽

Cited By ~ 4

Author(s):

Songtao Ai ◽

Xi Ding ◽

Jiachun An ◽

Guobiao Lin ◽

Zemin Wang ◽

...

Keyword(s):

Flow Velocity ◽

Flow Line ◽

Flow Region ◽

Field Work ◽

High Arctic ◽

Ice Flow ◽

Warming Climate ◽

Central Flow

Ice flow velocity is a sensitive indicator of glacier variations both controlling and representing the delivery of ice and affecting the future stability of ice masses in a warming climate. As one of the poly-thermal glaciers in the high Arctic, Austre Lovénbreen (AL) is on the northwestern coast of Spitsbergen, Svalbard. The ice flow velocity of AL was investigated using in situ global positioning system (GPS) observations over 14 years and numerical modelling with Elmer/Ice. First, the ice flow velocity field of AL along central flow line was presented and the ice flow velocity is approximately 4 m/a. Obvious seasonal changes of ice flow velocity can be found in the middle of the glacier, where the velocity in spring-summer is 47% larger than in autumn–winter in 2016, and the mean annual velocity increased 14% from 2009 until 2016. Second, the numerical simulation was performed considering the poly-thermal character of the glacier, and indicated that there are two peak ice flow regions on the glacier, and not just one peak ice flow region as previously believed. The new peak ice flow zone found by simulation was verified by field work, which also demonstrated that the velocity of the newly identified zone is 8% faster than the previously identified zone. Third, although our field observations showed that the ice flow velocity is slowly increasing recently, the maximum ice flow velocity will soon begin to decrease gradually in the long term according to glacier evolution modelling of AL.

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Some Possible Causes For Recent Variations Of Patagonian Glaciers

Annals of Glaciology ◽

10.1017/s0260305500009228 ◽

1990 ◽

Vol 14 ◽

pp. 351 ◽

Cited By ~ 2

Author(s):

Renji Naruse ◽

Masamu Aniya

Keyword(s):

Flow Velocity ◽

Air Temperature ◽

Water System ◽

Large Change ◽

Heavy Precipitation ◽

Field Studies ◽

Melting Rate ◽

Velocity Variation ◽

Ice Flow ◽

San Rafael

The Patagonian glaciers located in the southern part of the Andes between 46°30′S and 51°30′S are characterized by typical temperate conditions of heavy precipitation, rapid ice flows and high melting rates. During the austral summers of 1983–84 and 1985–86, field studies were made of the ice flow, heat balance and morphology of several glaciers in Patagonia. Coupled with aerial photographic surveys, these revealed that most glaciers had retreated extensively in the recent years, a maximum being 200 m a-1 at San Rafael Glacier from 1974 to 1986. The lower part of Soler Glacier had thinned by a rate of 5.2 m a-1 from 1983 to 1985. This paper presents three possible mechanisms to explain the large variation of temperate glaciers during the last decade, based on analyses of mass balance and dynamics of Patagonian glaciers: (1) The annual melting rate was estimated at about 10–15 m a-1 in water equivalent over the ablation area (from 350 to 1350 m a.s.l.) of Soler Glacier. Monthly mean air temperature in the coldest season (June through August) was estimated at about 0°–4°C near the termini of most glaciers in Patagonia. That temperature coincides with an air temperature which is critical for solid or liquid precipitation. The difference in the surface albedo, that is, 0.7–0.8 for new snow and 0.4–0.55 for bare ice (0.1–0.2 for debris-covered ice), results in different melting rates. Hence, a slight change in air temperature should cause an enhanced change in ice thickness by a positive feedback mechanism. (2) The flow velocity was measured or estimated and was found to change daily and seasonally by factors of 3 to 5 at Soler Glacier. The large flow velocity variation was attributed to difference in the basal sliding velocity. Consequently, a change in the amount of subglacial water or the structure of the basal water system should cause a large change in the ice flow, which in turn results in a retreat or an advance of the glacier-like “mini-surge”. (3) Frequent fluctuations of calving glaciers (e.g. San Rafael and Pio XI glaciers) have been much reported; however, information on the position of the grounding lines is very scarce. The advance or retreat of the glacier front may possibly have been affected by that of the floating terminus. The rate of calving from the ice tongue or spreading of ice shelves should mainly be controlled by the melting rate of ice in the water and by the mechanical properties of ice, and these factors are not directly related to climatic change or the surge phenomenon.

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Some Possible Causes For Recent Variations Of Patagonian Glaciers

Annals of Glaciology ◽

10.3189/s0260305500009228 ◽

1990 ◽

Vol 14 ◽

pp. 351-351 ◽

Cited By ~ 1

Author(s):

Renji Naruse ◽

Masamu Aniya

Keyword(s):

Flow Velocity ◽

Air Temperature ◽

Water System ◽

Large Change ◽

Heavy Precipitation ◽

Field Studies ◽

Melting Rate ◽

Velocity Variation ◽

Ice Flow ◽

San Rafael

The Patagonian glaciers located in the southern part of the Andes between 46°30′S and 51°30′S are characterized by typical temperate conditions of heavy precipitation, rapid ice flows and high melting rates. During the austral summers of 1983–84 and 1985–86, field studies were made of the ice flow, heat balance and morphology of several glaciers in Patagonia. Coupled with aerial photographic surveys, these revealed that most glaciers had retreated extensively in the recent years, a maximum being 200 m a-1 at San Rafael Glacier from 1974 to 1986. The lower part of Soler Glacier had thinned by a rate of 5.2 m a-1 from 1983 to 1985.This paper presents three possible mechanisms to explain the large variation of temperate glaciers during the last decade, based on analyses of mass balance and dynamics of Patagonian glaciers:(1) The annual melting rate was estimated at about 10–15 m a-1 in water equivalent over the ablation area (from 350 to 1350 m a.s.l.) of Soler Glacier. Monthly mean air temperature in the coldest season (June through August) was estimated at about 0°–4°C near the termini of most glaciers in Patagonia. That temperature coincides with an air temperature which is critical for solid or liquid precipitation. The difference in the surface albedo, that is, 0.7–0.8 for new snow and 0.4–0.55 for bare ice (0.1–0.2 for debris-covered ice), results in different melting rates. Hence, a slight change in air temperature should cause an enhanced change in ice thickness by a positive feedback mechanism.(2) The flow velocity was measured or estimated and was found to change daily and seasonally by factors of 3 to 5 at Soler Glacier. The large flow velocity variation was attributed to difference in the basal sliding velocity. Consequently, a change in the amount of subglacial water or the structure of the basal water system should cause a large change in the ice flow, which in turn results in a retreat or an advance of the glacier-like “mini-surge”.(3) Frequent fluctuations of calving glaciers (e.g. San Rafael and Pio XI glaciers) have been much reported; however, information on the position of the grounding lines is very scarce. The advance or retreat of the glacier front may possibly have been affected by that of the floating terminus. The rate of calving from the ice tongue or spreading of ice shelves should mainly be controlled by the melting rate of ice in the water and by the mechanical properties of ice, and these factors are not directly related to climatic change or the surge phenomenon.

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Review of: Greenland Ice Mapping Project: Ice Flow Velocity Variation at submonthly to decadal time scales

10.5194/tc-2018-40-rc2 ◽

2018 ◽

Author(s):

Anonymous

Keyword(s):

Flow Velocity ◽

Time Scales ◽

Velocity Variation ◽

Ice Flow

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Corner Reflectors for Validation of Ice Flow Velocity Derived from SAR Images along the CHINARE-Route in Antarctica

10.5194/egusphere-egu2020-18221 ◽

2020 ◽

Author(s):

Gang Qiao ◽

Rongxing Li ◽

Tong Hao ◽

Xiaohua Tong ◽

Yanjun Li ◽

...

Keyword(s):

Mass Balance ◽

Flow Velocity ◽

Incident Angle ◽

Surface Shape ◽

Sar Images ◽

Ice Flow ◽

Ground Truth Data ◽

Radar Images ◽

Ice Velocity

Ice flow velocity is an important parameter for evaluating the stability of Antarctic ice shelves and analyzing the mass balance of the ice sheet. Large scale ice flow maps can be produced from satellite images with ground control and validation. Among various ground targets, corner reflectors show distinct intensity characteristics on SAR images due to its highly reflective surface shape and have been used for calibration and validation. This paper focuses on design and implementation of a set of corner reflectors to obtain the first-hand data of in-situ ice flow velocity for SAR image based ice velocity maps. The results should further help evaluate mass balance changes in East Antarctica using the input-output method.Generally, the remote sensing method uses airborne or satellite optical and radar images from multiple periods to map ice flow velocity fields. The ground truth data are often sparse due to the harsh environment in the polar region. The annual Chinese Antarctic Research Expedition (CHINARE) makes it possible to obtain period field data of ice velocity within its campaign regions. The ~1200 km CHINARE-Route runs from Zhongshan Station to Kunlun Station along which the ice flow velocity varies from a few meters per year to 100s meters per year. 5 corner reflectors have been designed and installed along the 31st CHINARE-Route in 2015 and the 35th CHINARE-Route in 2019 (M1, M2 and M3 in the 31st CHINARE, A1and A2 in the 35th CHINARE). The ice flow velocities at the installation locations are of different orders of magnitude, about 44 m per year at the locations of M1 and A1, 93 m per year at M2 and M3 and 73 m per year at A2. The satellite orbit inclination, incident angle and the installation location were used to calculate the azimuth and elevation angles of the corner reflectors for installation. At all reflector locations GPS positions were collected at the time of installation. After that, the second time GPS coordinates of M3 in the 34th CHINARE in 2018, the third time GPS coordinates of M3, the second time GPS coordinates of A1 and A2 in the 36th CHINARE at the end of 2019 were measured respectively. TerraSAR-X was used to image the reflectors.The results show that the mean in-situ ice flow velocity of M3 is 96.83 m per year between Feb. 2015 and Dec. 2019, with 97.51 m per year between Feb. 2015 and Jan. 2018 and 95.81m per year between Jan. 2018 and Dec. 2019. The in-situ ice flow velocity is 54.9 m per year at A1 between Jan. 2019 and Dec. 2019 and 86.92 m per year at A2 between Feb. 2019 and Dec. 2019. More TerraSAR-X and COSMO-SkyMed data will be used to extract the ice velocity corresponding to GPS measurements. The detailed information will be presented at the meeting.

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