Outlet Glacier Dynamics in East Greenland and East Antarctica

Ice mass from the interior of Greenland and Antarctica is transported to the ocean by numerous large, fast-flowing outlet glaciers. Changes in the flow configuration of these outlet glaciers modulate ice sheet mass balance and sea level. Several recent studies have highlighted rapid increases in glacier speed in both Greenland and Antarctica, implying that the near-term contribution to sea level from ice sheets is under-estimated by current models. Here, the mass balance and force budget of several large outlet glaciers in East Greenland and East Antarctica are investigated using remote-sensing and field-based measurements. Recent estimates show that Greenland’s contribution to sea level more than doubled in the past decade, and that the majority of this additional mass loss is due to changes in the dynamics of a few large outlet glaciers. Our measurements indicate that up to ~10% of global sea level rise over the period 2001 – 2006 was contributed by just two glaciers, Helheim and Kangerdlugssuaq, in Southeast Greenland. We also find a latitudinal pattern of glacier behavior in East Greenland, where large and rapid changes are taking place south of 70°N while glaciers north of 70°N are stable. The East Antarctic Ice Sheet is Earth’s largest source of freshwater and has the potential to raise sea level by 57 m. The dynamics of outlet glaciers draining the ice sheet through the Transantarctic Mountains are largely unknown, but the glaciers are often assumed to be stable. In this study we investigate the dynamics of four large East Antarctic outlet glaciers. Together, these glaciers drain ~1,500,000 km2, or 12% by area of the entire Antarctic Ice Sheet. Mass balance calculations show modest imbalances for some glaciers, and a large imbalance for Byrd Glacier. Observations indicate a possible recent increase in flow speed, but this is insufficient to explain the large imbalance. We argue that catchment–wide estimates of accumulation rate contain large errors. This research provides new insights into the dynamic character of ice sheet outlet glaciers. In addition to quantifying recent changes, it also provides baseline data against which future behavior can be assessed

A New Velocity Map for Byrd Glacier, East Antarctica, from Sequential Aster Satellite Imagery

New ice-velocity measurements are obtained for the main trunk of Byrd Glacier, East Antarctica, using recently acquired Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. The velocities are derived from the application of a cross-correlation technique to sequential images acquired in 2000 and 2001. Images were co-registered and ortho-rectified with the aid of a digital elevation model (DEM) generated from ASTER stereo imagery. This paper outlines the process of DEM generation, image co-registration and correction, and the application of the cross-correlation technique to obtain ice velocities. Comparison of the new velocity map with earlier measurements of velocity from 1978 indicates that the glacier has undergone a substantial deceleration between observations. Portions of the glacier flowing at speeds of similar to 850 m a(-1) in 1978/79 were flowing at similar to 650 m a(-1) in 2000/01. The cause of this change in ice dynamics is not known, but the observation shows that East Antarctic outlet glaciers can undergo substantial changes on relatively short timescales

Quantification and Analysis of Icebergs Distribution around Greenland ussing Sentinel SAR images

This presentation was given as part of the GIS Day@KU symposium on November 16, 2016. For more information about GIS Day@KU activities, please see http://gis.ku.edu/gisday/2016/.Platinum Sponsors: KU Department of Geography and Atmospheric Science. Gold Sponsors: Enertech, KU Environmental Studies Program, KU Libraries. Silver Sponsors: Douglas County, Kansas, KansasView, State of Kansas Data Access & Support Center (DASC) and the KU Center for Global and International Studies

Quantifying Iceberg Distribution in Rink Fjord using Satellite Remote Sensing

This presentation was given as part of the GIS Day@KU symposium on November 18, 2015. For more information about GIS Day@KU activities, please see http://www.gis.ku.edu/gisday/2015/.Platinum Sponsors: KU Department of Geography and Atmospheric Science; KU School of Business. Gold Sponsors: Bartlett & West; Kansas Biological Survey; KU Environmental Studies Program; KU Institute for Policy & Social Research; KU Libraries. Silver Sponsors: State of Kansas Data Access and Support Center (DASC). Bronze Sponsors: KU Center for Remote Sensing of Ice Sheets (CReSIS); TREKK Design Group, LLC; Wilson & Company, Engineers and Architects

Estimating River Surface Velocity Using Optical Remote Sensing Techniques

This presentation was given as part of the GIS Day@KU symposium on November 18, 2015. For more information about GIS Day@KU activities, please see http://www.gis.ku.edu/gisday/2015/.Platinum Sponsors: KU Department of Geography and Atmospheric Science; KU School of Business. Gold Sponsors: Bartlett & West; Kansas Biological Survey; KU Environmental Studies Program; KU Institute for Policy & Social Research; KU Libraries. Silver Sponsors: State of Kansas Data Access and Support Center (DASC). Bronze Sponsors: KU Center for Remote Sensing of Ice Sheets (CReSIS); TREKK Design Group, LLC; Wilson & Company, Engineers and Architects

Rapid volume loss from two East Greenland outlet glaciers quantified using repeat stereo satellite imagery

This is the publisher's version, also available electronically from "http://onlinelibrary.wiley.com/".[1] The coastal portions of Kangerdlugssuaq and Helheim glaciers in southeast Greenland lost at least 51 ± 8 km3 yr−1 of ice between 2001–2006 due to thinning and retreat, according to an analysis of sequential digital elevation models (DEMs) derived from stereo ASTER satellite imagery. The dominant contribution to this ice loss was dynamic thinning caused by the acceleration in flow of both glaciers. Peak rates of change, including thinning rates of ∼90 m yr−1, coincided with the rapid increases in flow speed. Extrapolation of the measured data to the ice divides yields an estimated combined catchment volume loss of ∼122 ± 30 km3 yr−1, which accounts for half the total mass loss from the ice sheet reported in recent studies. These catchment-wide volume losses contributed ∼0.31 ± 0.07 mm yr−1 to global sea level rise over the 5-year observation period with the coastal regions alone contributing at least 0.1 ± 0.02 mm yr−1

Rapid Volume Loss from Two East Greenland Outlet Glaciers Quantified Using Repeat Stereo Satellite Imagery

The coastal portions of Kangerdlugssuaq and Helheim glaciers in southeast Greenland lost at least 51 +/- 8 km(-3) yr(-1) of ice between 2001-2006 due to thinning and retreat, according to an analysis of sequential digital elevation models (DEMs) derived from stereo ASTER satellite imagery. The dominant contribution to this ice loss was dynamic thinning caused by the acceleration in flow of both glaciers. Peak rates of change, including thinning rates of similar to 90 m yr(-1), coincided with the rapid increases in flow speed. Extrapolation of the measured data to the ice divides yields an estimated combined catchment volume loss of similar to 122 +/- 30 km(-3) yr(-1), which accounts for half the total mass loss from the ice sheet reported in recent studies. These catchment-wide volume losses contributed similar to 0.31 +/- 0.07 mm yr(-1) to global sea level rise over the 5-year observation period with the coastal regions alone contributing at least 0.1 +/- 0.02 mm yr(-1)

Impact of ocean stratification on submarine melting of a major Greenland outlet glacier

Submarine melting is an important balance term for tidewater glaciers1,2 and recent observations point to a change in the submarine melt rate as a potential trigger for the widespread acceleration of outlet glaciers in Greenland3-5. Our understanding of the dynamics involved, and hence our ability to interpret past and predict future variability of the Greenland Ice Sheet, however, is severely impeded by the lack of measurements at the ice/ocean interface. To fill this gap, attempts to quantify the submarine melt rate and its variability have relied on a paradigm developed for tidewater glaciers terminating in fjords with shallow sills. In this case, the fjords’ waters are mostly homogeneous and the heat transport to the terminus, and hence the melt rate, is controlled by a single overturning cell in which glacially modified water upwells at the ice edge, driving an inflow at depth and a fresh outflow at the surface1. Greenland’s fjords, however, have deep sills which allow both cold, fresh Arctic and warm, salty Atlantic waters, circulating around Greenland, to reach the ice sheet margin3,6,7. Thus, Greenland’s glaciers flow into strongly stratified fjords and the generic tidewater glacier paradigm is not applicable. Here, using new summer data collected at the margins of Helheim Glacier, East Greenland, we show that melting is driven by both Atlantic and Arctic waters and that the circulation at the ice edge is organized in multiple, overturning cells that arise from their different properties. Multiple cells with different characteristics are also observed in winter, when glacial run off is at a minimum and there is little surface outflow. These results indicate that stratification in the fjord waters has a profound impact on the melting dynamics and suggest that the shape and stability of Greenland’s glaciers are strongly influenced by layering and variability in the Arctic and Atlantic waters. 

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Spatial Patterns in Mass Balance of the Siple Coast and Amundsen Sea Sectors, West Antarctica

Local rates of change in ice-sheet thickness were calculated at IS sites in West Antarctica using the submergence velocity technique. This method entails a comparison of the vertical velocity of the ice sheet, measured using repeat global positioning system surveys of markers, and local long-term rates of snow accumulation obtained using firn-core stratigraphy. Any significant difference between these two quantities represents a thickness change with time. Measurements were conducted at sites located similar to 100-200 km apart along US ITASE traverse routes, and at several isolated locations. All but one of the sites are distributed in the Siple Coast and the Amundsen Sea basin along contours of constant elevation, along flowlines, across ice divides and close to regions of enhanced flow. Calculated rates of thickness change are different from site to site. Most of the large rates of change in ice thickness (similar to 10 cm a(-1) or larger) are observed in or close to regions of rapid flow, and are probably related to ice-dynamics effects. Near-steady-state conditions are calculated mostly at sites in the slow-moving ice-sheet interior and near the main West Antarctic ice divide. These results are consistent with regional estimates of ice-sheet change derived from remote-sensing measurements at similar locations in West Antarctica

Temporal Analysis of Ice Thickness at Byrd Glacier's Grounding Zone

This presentation was given as part of the GIS Day@KU symposium on November 16, 2016. For more information about GIS Day@KU activities, please see http://gis.ku.edu/gisday/2016/.Platinum Sponsors: KU Department of Geography and Atmospheric Science. Gold Sponsors: Enertech, KU Environmental Studies Program, KU Libraries. Silver Sponsors: Douglas County, Kansas, KansasView, State of Kansas Data Access & Support Center (DASC) and the KU Center for Global and International Studies