scholarly journals Hydrological and Kinematic Precursors of the 2017 Calving Event at the Petermann Glacier in Greenland Observed from Multi-Source Remote Sensing Data

2021 ◽  
Vol 13 (4) ◽  
pp. 591
Author(s):  
Daan Li ◽  
Liming Jiang ◽  
Ronggang Huang
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Remote Sensing Data ◽  
Open Water ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Backscatter Coefficient ◽  
Sea Ice Extent ◽  
Ice Flow ◽  
Glacier Velocity

Both a decrease of sea ice and an increase of surface meltwater, which may induce ice-flow speedup and frontal collapse, have a significant impact on the stability of the floating ice shelf in Greenland. However, detailed dynamic precursors and drivers prior to a fast-calving process remain unclear due to sparse remote sensing observations. Here, we present a comprehensive investigation on hydrological and kinematic precursors before the calving event on 26 July 2017 of Petermann Glacier in northern Greenland, by jointly using remote sensing observations at high-temporal resolution and an ice-flow model. Time series of ice-flow velocity fields during July 2017 were retrieved with Sentinel-2 observations with a sub-weekly sampling interval. The ice-flow speed quickly reached 30 m/d on 26 July (the day before the calving), which is roughly 10 times quicker than the mean glacier velocity. Additionally, a significant decrease in the radar backscatter coefficient of Sentinel-1 images suggests a rapid transformation from landfast sea ice into open water, associated with a decrease in sea ice extent. Additionally, the area of melt ponds on the floating ice tongue began to increase in mid-May, quickly reached a peak at the end of June and lasted for nearly one month until the calving occurred. We used the ice sheet system model to model the spatial-temporal damage and stress on the floating ice, thereby finding an abnormal stress distribution in a cracked region. It is inferred that this calving event may relate to a weakening of the sea ice, shearing of the tributary glacier, and meltwater infiltrating crevasses.

Hydrological and Kinematic Precursors of Iceberg Calving at Petermann Glacier in Northern Greenland Observed High-temporal Resolution Sentinel-2 Images

2020 ◽  
Author(s):  
Daan Li ◽  
Liming Jiang
Keyword(s):  
Remote Sensing ◽  
High Resolution ◽  
Sea Ice ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Backscatter Coefficient ◽  
Ice Flow ◽  
Iceberg Calving

<p>   The Greenland ice sheet is currently contributing to global sea level at an approximate rate of 0.8 mm/yr. Ice mass loss of Greenland is primarily due to both thinning and retreat of outlet glaciers. For enhanced calving events, detail dynamics characteristics of hydrological and kinematic precursors and underlying mechanisms which control the development of ice calving remain poorly understood, especially in the absence of high-resolution remote sensing observations. On July 26 2017, a calving event took place along a pre-existing rift in Petermann glacier, northern Greenland, which removed partly of the glacier tongue and formed a tabular iceberg 5 km long. In this study, we used high-temporal satellite remote sensing data to detect changes in ice-flow speed, melt ponds and ice mélange during May and July. These hydrological and kinematic dynamics derived from Sentinel-1/2 satellite images with sub-weekly acquisition repeat cycles can be utilized as retreat precursors to characterize the detailed calving process. Moreover, the stress field and analytical damage solution were calculated by coupling the remote sensing observations with SSA ice sheet model to explain the dynamics mechanism. Our preliminary results show that the ice speed in dense observation reached to 30 m/d on the eve of the calving, which is roughly 10 times quicker than usual ice velocity. Additionally, there exited obviously abnormal stress distribution in crack region. And the landfast sea ice and ice mélange transformed into open water that the  backscatter coefficient decreased to 28 dB. The extent of melt pond reached the peak about 30 square kilometers coverage in duration month of calving event. It is inferred that this calving event of Petermann glacier may be related to weakening of sea ice and ice mélange lost the buttressing for ice glacier terminate, tributary glacier extrusion, related with meltwater infiltrated crevasses. Therefore, dense remote sensing observations and numerical modeling in ice flow system make it possible for early waring and projecting glacier calving in the future.</p><p>Key words: Iceberg Calving Precursors, Petermann Glacier, High Resolution Remote Sensing, SSA modeling</p>

scholarly journals Towards multi-sensor microwave remote sensing of frost flowers on sea ice

2004 ◽  
Vol 39 ◽  
pp. 219-222 ◽  
Author(s):  
Lars Kaleschke ◽  
Georg Heygster
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Ice Core ◽  
Remote Sensing Data ◽  
Microwave Remote Sensing ◽  
Open Water ◽  
Tropospheric Chemistry ◽  
Backscatter Signal ◽  
Additional Information ◽  
Frost Flowers

AbstractIt has been hypothesized that frost flowers could be important for tropospheric chemistry and, as a source of sea-salt aerosol, for the interpretation of ice-core data. Furthermore, frost flowers can cause severe errors in sea-ice products derived from remote-sensing data. Up to now there have been few datasets available relating frost-flower distribution and variability in the sea-ice-covered regions. We present a method for frost-flower detection using a combination of active and passive microwave sensors. The vertical polarized C-band radar backscatter of a young sea-ice region covered with frost flowers can be higher than the signal from multi-year ice or from the wind-roughened ocean. Therefore, the classification result of synthetic aperture radar (SAR) sea-ice images can be defective due to the influence of frost flowers. The ambiguity of the open-water and frost-flower backscatter signal was successfully resolved using additional information from the 85 GHz Special Sensor Microwave/Imager (SSM/I) channels. Results of the method were compared to aircraft measurements and observations in the marginal ice zone near Svalbard.

scholarly journals Characteristics of The Seasonal Sea Ice of East Antarctica and Comparisons with Satellite Observations

1987 ◽  
Vol 9 ◽  
pp. 85-91 ◽  
Author(s):  
T.H. Jacka ◽  
I. Allison ◽  
R. Thwaites ◽  
J.C. Wilson
Keyword(s):  
Sea Ice ◽  
Remote Sensing Data ◽  
Ice Cores ◽  
Open Water ◽  
Early Spring ◽  
Visual Channel ◽  
Antarctic Waters ◽  
Study Characteristics ◽  
Satellite Sensors ◽  
The Antarctic

A cruise to Antarctic waters from late October to mid December 1985 provided the opportunity to study characteristics of the seasonal sea ice from a time close to that of maximum extent through early spring decay. The area covered by the observations extends from the northern ice limit to the Antarctic coast between long. 50 °E and 80 E. Shipboard observations included ice extent, type and thickness, and snow depth. Ice cores were drilled at several sites, providing data on salinity and structure.The observations verify the highly dynamic and divergent nature of the Antarctic seasonal sea-ice 2one. Floe size and thickness varied greatly at all locations, although generally increasing from north to south. A high percentage of the total ice mass exhibited a frazil crystal structure, indicative of the existence of open water in the vicinity.The ground based observations are compared with observations from satellite sensors. The remote sensing data include the visual channel imagery from NOAA 6, NOAA 9, and Meteor 11. Comparisons are made with the operational ice charts produced (mainly from satellite data) by the Joint Ice Center, and with the analyses available by facsimile from Molodezhnaya.

scholarly journals Brief communication: lack of agreement in remote sensing detection of cyclonic drift caused by Atlantic weather in Antarctic sea ice

2021 ◽  
Author(s):  
Wayne de Jager ◽  
Marcello Vichi
Keyword(s):  
Remote Sensing ◽  
Sea Ice ◽  
Alternative Methods ◽  
Polar Regions ◽  
Sea Ice Concentration ◽  
Sea Ice Extent ◽  
Ice Dynamics ◽  
Antarctic Sea Ice ◽  
Ice Drift ◽  
The Impact

Abstract. Sea-ice extent variability, a measure based on satellite-derived sea ice concentration measurements, has traditionally been used as an essential climate variable to evaluate the impact of climate change on polar regions. However, concentration- based measurements of ice variability do not allow to discriminate the relative contributions made by thermodynamic and dynamic processes, prompting the need to use sea-ice drift products and develop alternative methods to quantify changes in sea ice dynamics that would indicate trends in Antarctic ice characteristics. Here, we present a new method to automate the detection of rotational drift features in Antarctic sea ice at daily timescales using currently available remote sensing ice motion products from EUMETSAT OSI SAF. Results show that there is a large discrepancy in the detection of cyclonic drift features between products, both in terms of intensity and year-to-year distributions, thus diminishing the confidence at which ice drift variability can be further analysed. Product comparisons showed that there was good agreement in detecting anticyclonic drift, and cyclonic drift features were measured to be 1.5–2.2 times more intense than anticyclonic features. The most intense features were detected by the merged product, suggesting that the processing chain used for this product could be injecting additional rotational momentum into the resultant drift vectors. We conclude that it is therefore necessary to better understand why the products lack agreement before further trend analysis of these drift features and their climatic significance can be assessed.

Large-scale Arctic sea ice motion from Sentinel-1 and the RADARSAT Constellation Mission

2021 ◽  
Author(s):  
Stephen Howell ◽  
Mike Brady ◽  
Alexander Komarov
Keyword(s):  
Sea Ice ◽  
Spatial Resolution ◽  
Temporal Resolution ◽  
Large Scale ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
High Temporal Resolution ◽  
Sar Images ◽  
Sea Ice Extent ◽  
Arctic Sea

<p>As the Arctic’s sea ice extent continues to decline, remote sensing observations are becoming even more vital for the monitoring and understanding of this process.  Recently, the sea ice community has entered a new era of synthetic aperture radar (SAR) satellites operating at C-band with the launch of Sentinel-1A in 2014, Sentinel-1B in 2016 and the RADARSAT Constellation Mission (RCM) in 2019. These missions represent a collection of 5 spaceborne SAR sensors that together can routinely cover Arctic sea ice with a high spatial resolution (20-90 m) but also with a high temporal resolution (1-7 days) typically associated with passive microwave sensors. Here, we used ~28,000 SAR image pairs from Sentinel-1AB together with ~15,000 SAR images pairs from RCM to generate high spatiotemporal large-scale sea ice motion products across the pan-Arctic domain for 2020. The combined Sentinel-1AB and RCM sea ice motion product provides almost complete 7-day coverage over the entire pan-Arctic domain that also includes the pole-hole. Compared to the National Snow and Ice Data Center (NSIDC) Polar Pathfinder and Ocean and Sea Ice-Satellite Application Facility (OSI-SAF) sea ice motion products, ice speed was found to be faster with the Senintel-1AB and RCM product which is attributed to the higher spatial resolution of SAR imagery. More sea ice motion vectors were detected from the Sentinel-1AB and RCM product in during the summer months and within the narrow channels and inlets compared to the NSIDC Polar Pathfinder and OSI-SAF sea ice motion products. Overall, our results demonstrate that sea ice geophysical variables across the pan-Arctic domain can now be retrieved from multi-sensor SAR images at both high spatial and temporal resolution.</p>

scholarly journals Contrasts in the response of adjacent fjords and glaciers to ice-sheet surface melt in West Greenland

2016 ◽  
Vol 57 (73) ◽  
pp. 25-38 ◽  
Author(s):  
Timothy C. Bartholomaus ◽  
Leigh A. Stearns ◽  
David A. Sutherland ◽  
Emily L. Shroyer ◽  
Jonathan D. Nash ◽  
...  
Keyword(s):  
Satellite Remote Sensing ◽  
Heat Content ◽  
Flow Speed ◽  
High Temporal Resolution ◽  
Glacier Surface ◽  
Ice Flow ◽  
Tidewater Glaciers ◽  
Circulation Patterns ◽  
Key Factor ◽  
Surface Melt

ABSTRACTNeighboring tidewater glaciers often exhibit asynchronous dynamic behavior, despite relatively uniform regional atmospheric and oceanic forcings. This variability may be controlled by a combination of local factors, including glacier and fjord geometry, fjord heat content and circulation, and glacier surface melt. In order to characterize and understand contrasts in adjacent tidewater glacier and fjord dynamics, we made coincident ice-ocean-atmosphere observations at high temporal resolution (minutes to weeks) within a 10 000 km2 area near Uummannaq, Greenland. Water column velocity, temperature and salinity measurements reveal systematic differences in neighboring fjords that imply contrasting circulation patterns. The observed ocean velocity and hydrography, combined with numerical modeling, suggest that subglacial discharge plays a major role in setting fjord conditions. In addition, satellite remote sensing of seasonal ice flow speed and terminus position reveal both speedup and slow-down in response to melt, as well as differences in calving style among the neighboring glaciers. Glacier force budgets and modeling also point toward subglacial discharge as a key factor in glacier behavior. For the studied region, individual glacier and fjord geometry modulate subglacial discharge, which leads to contrasts in both fjord and glacier dynamics.

scholarly journals Grounding and calving cycle of Mertz Ice Tongue revealed by shallow Mertz Bank

2016 ◽  
Vol 10 (5) ◽  
pp. 2043-2056 ◽  
Author(s):  
Xianwei Wang ◽  
David M. Holland ◽  
Xiao Cheng ◽  
Peng Gong
Keyword(s):  
Remote Sensing ◽  
Flow Direction ◽  
Remote Sensing Data ◽  
Sea Surface ◽  
Seafloor Topography ◽  
Ice Flow ◽  
Air Content ◽  
Cyclic Variations ◽  
Cyclical Process ◽  
Height Data

Abstract. A recent study, using remote sensing, provided evidence that a seafloor shoal influenced the 2010 calving event of the Mertz Ice Tongue (MIT), by partially grounding the MIT several years earlier. In this paper, we start by proposing a method to calculate firn air content (FAC) around Mertz from seafloor-touching icebergs. Our calculations indicate the FAC around Mertz region as 4.87 ± 1.31 m. We then design an indirect method of using freeboard and sea surface height data extracted from ICESat/GLAS, FAC, and relatively accurate seafloor topography to detect grounding sections of the MIT between 2002 and 2008 and analyze the process of grounding prior to the calving event. By synthesizing remote sensing data, we point out that the grounding position was localized northeast of the Mertz ice front close to the Mertz Bank. The grounding outlines of the tongue caused by the Mertz Bank are extracted as well. From 2002 to 2008, the grounding area increased and the grounding became more pronounced. Additionally, the ice tongue could not effectively climb over the Mertz Bank in following the upstream ice flow direction and that is why MIT rotated clockwise after late 2002. Furthermore, we demonstrate that the area-increasing trend of the MIT changed little after calving (∼  36 km2 a−1), thus allowing us to use remote sensing to estimate the elapsed time until the MIT can reground on and be bent by the shoal. This period is approximately 70 years. Our observations suggest that the calving of the MIT is a cyclical process controlled by the presence of the shallow Mertz Bank location and the flow rate of the tongue. This calving cycle also explains the cyclic variations in sea-surface conditions around the Mertz detected by earlier studies.

scholarly journals In-situ measurements of the ice flow motion at Eqip Sermia Glacier using a remotely controlled UAV

2019 ◽  
Author(s):  
Guillaume Jouvet ◽  
Eef van Dongen ◽  
Martin P. Lüthi ◽  
Andreas Vieli
Keyword(s):  
Remote Sensing ◽  
Template Matching ◽  
In Situ Measurements ◽  
In Situ Monitoring ◽  
High Temporal Resolution ◽  
Ice Flow ◽  
Flow Motion ◽  
Remote Sensing Techniques ◽  
Matching Techniques

Abstract. Measuring the ice flow motion accurately is essential to better understand the time evolution of glaciers and ice sheets, and therefore to better anticipate the future consequence of climate change in terms of sea-level rise. Although there exist a variety of remote sensing methods to fill this task, in-situ measurements are always needed for validation or to capture high temporal resolution movements. Yet glaciers are in general hostile environments where the installation of instruments might be tedious and risky when not impossible. Here we report the first-ever in-situ measurements of ice flow motion using a remotely controlled Unmanned Aerial Vehicle (UAV). We used a multicopter UAV to land on a highly crevassed area of Eqip Sermia Glacier, West Greenland, to measure the displacement of the glacial surface with the aid of an on-board differential GNSS receiver. Despite the unfortunate loss of the UAV, we measured approximately 70 cm of displacement over 4.36 hours without setting foot onto the glacier – a result validated by applying UAV photogrammetry and template matching techniques. Our study demonstrates that UAVs are promising instruments for in-situ monitoring, and have a great potential for capturing short-term ice flow variations in inaccessible glaciers – a task that remote sensing techniques can hardly achieve.

scholarly journals Evaluation of Geospatial Tools for Generating Accurate Glacier Velocity Maps from Optical Remote Sensing Data

Proceedings ◽  
2018 ◽  
Vol 2 (7) ◽  
pp. 341 ◽  
Author(s):  
Shridhar D. Jawak ◽  
Shubhang Kumar ◽  
Alvarinho J. Luis ◽  
Mustansir Bartanwala ◽  
Shravan Tummala ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Remote Sensing Data ◽  
Optical Remote Sensing ◽  
Sensing Data ◽  
Geospatial Tools ◽  
Glacier Velocity
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