C43C-0234 1340h
100 Years of Glacier Photographs: Available Online at the National Snow and Ice Data Center
Historic glacier photographs can be used to study fluctuations in glacier extent over time in response to climate change. Researchers can also use the photographs to approximate changes in glacier terminus location and mass balance. The "Glacier Photograph Collection" at the National Snow and Ice Data Center (NSIDC) contains approximately 5,000 photographs, including both aerial and terrestrial images. NSIDC received funding from the NOAA Climate Database Modernization Program (CDMP) to digitize a portion of the photographs and make an Online Glacier Photograph Database available. The CDMP's primary objective is to preserve climate data and facilitate access to the data. Although digitizing images is expensive, long-term data preservation is a major benefit. When historic photographs are stored on film, images can easily be scratched or damaged. Scanning the images and having them online makes browsing images easier for users. At present, there are 1,313 glacier photographs available online. Additional photos and metadata are being added. The Online Glacier Photograph Database will date from 1883 to 1995, totaling nearly 3,000 photographs available as high resolution TIFF images and lower resolution reference images and thumbnails by the end of 2004. Maintaining accurate metadata records for each photograph is very important. The database is searchable by various fields, including photographer name, photograph date, glacier name, glacier coordinates, state/province, and keyword.
http://nsidc.org/data/g00472.html
C43C-0235 1340h
Use of Surface Oblique Photography to Estimate Melt Puddle Progression on Melting Fast Ice, Baffin Island NWT.
In 1973 and 1974 surface oblique photographs were acquired to document the progression of surface melt pond development on melting fast ice. The original analysis technique applied to these photographs consisted of a manual estimation of proportional area covered by melt ponds in each photograph, based on the geometry of oblique photography. Today, some 30 years later, the development of digital analysis tools can allow more detailed analysis of these photographs. New tools including scanning of the original photographs, image enhancement and classification tools, and photomodelling software were applied to these photos. This paper assesses the ability of these computer-based tools to extract additional data, and to speed the analysis process for similar studies.
C43C-0236 1340h
Automatic, Satellite-Linked "Webcams" as a Tool in Ice-Shelf and Iceberg Research.
Important dynamic events governing the behavior of ice shelves and icebergs are episodic in time and small in scale, making them difficult to observe. Traditional satellite imagery is acquired on a rigid schedule with coarse spatial resolution and this means that collisions between icebergs or the processes which create ice "melange" that fills detachment rifts leading to ice-shelf calving, to give examples, cannot be readily observed. To overcome the temporal and spatial gaps in traditional remote sensing, we have deployed cameras at locations in Antarctica where research is conducted on the calving and subsequent evolution of icebergs. One camera is located at the edge of iceberg C16 in the Ross Sea, and is positioned to capture visual imagery of collisions between C16 and neighboring B15A. The second camera is located within the anticipated detachment rift of a "nascent" iceberg on the Ross Ice Shelf. The second camera is positioned to capture visual imagery of the rift's propagation and the in-fill of ice melange, which constrains the mechanical influence of such rifts on the surrounding ice shelf. Both cameras are designed for connection to the internet (hence are referred to as "webcams") and possess variable image qualities and image-control technology. The cameras are also connected to data servers via the Iridium satellite telephone network and produce a daily image that is transmitted to the internet through the Iridium connection. Results of the initial trial deployments will be presented as a means of assessing both the techniques involved and the value of the scientific information acquired by these webcams. In the case of the iceberg webcam, several collisions between B15A and C16 were monitored over the period between January, 2003 and December, 2004. The time-lapse imagery obtained through this period showed giant "push mounds" of damaged firn on the edge and surface of the icebergs within the zones of contact as a consequence of the collisions. The push mounds were subsequently unstable, and calved as small scale ice debris soon after the collision, thereby returning the iceberg edge to a clean, vertical cliff-like appearance. A correlation between the iceberg collision record available from the webcam and data from a seismometer located on C16 is anticipated once the seismometer data is recovered. The webcam associated with the detachment rift of the nascent iceberg on the Ross Ice Shelf is planned to be deployed in early November, 2004. If results are available from this deployment, they too will be discussed.
C43C-0237 1340h
Glaciers in Kenai Fjords NP: Exploration and Change
In 1909, USGS geologists U.S. Grant and D. F. Higgins mapped and photographed all of the tidewater glaciers and many of the land-terminating outlet glaciers in what is now Kenai Fjords National Park, creating a thorough record of glacier terminus positions and heights. In August, 2004, with funding from the National Park Service and the USGS Earth Surface Dynamics Program, we conducted a new photo survey in Grant and Higgins' footsteps. We re-established 40 of their photo stations with a confidence level of approximately 5-30 feet. We located the sites by identifying foreground features and by analyzing the extent of overlap of mountain peaks in the 1909 photo backgrounds. WAAS-enabled GPS was used to determine the location of each station for future surveys. At each station, we took new photographs duplicating the field of view shown in the 1909 photographs and also showing panoramic views. At most locations, the change in glacier height and terminus position since 1909 has been dramatic. At several stations, glacier termini were no longer visible. Northwestern Glacier, for example, has retreated around a series of bends in its valley. In some cases, vegetation completely obstructed the view from the 1909 photo station. In these instances, new GPS-located photo stations were established within sight of the present day termini. To illustrate the changes for the public, a dozen photographic pairs have been turned into animated GIFs using MacroMedia Flash. Each animation begins with a 1909 Grant and Higgins photograph which fades into the 2004 image. The two images have been correlated by matching topographic features. The animations clearly depict changes in vegetation, glacier cover, and geomorphologic features that have taken place in the last 95 years.
C43C-0238 1340h
Photographic Snow-cover Monitoring on St Sorlin Glacier, France.
Like most other glaciers in the Alps, the St Sorlin glacier (french Alps, 45.16°N, 6.16°E, 2900 m asl mean elevation and 3km2 of surface area) has been retreating fast in the last 20 years. To understand the meteorological factors responsible for this retreat, and to tentatively predict glaciers evolution in a changing (warming) climate, we use a distributed snow/ice mass and energy balance model derived from the CROCUS snow model (M,t,o-France). There is no direct meteorological observation on or near St Sorlin glacier yet, and hourly meteorology to force the snow/ice model is obtained from disaggregated meteorological analyses. The model is found to reproduce the St Sorlin mass balance of the last 20 years as obtained from field glaciological measurements and stereophotographic reconstructions. The model is also found to reproduce the interannual variations of the equilibrium line as determined from optical satellite imagery. Because of the albedo feedback involved, it is also important to verify that the summer snow/ice transition on the glacier is correctly simulated. Thus, an automated photographic system was set up facing St Sorlin glacier to monitor the evolution of the snow cover. The system was installed on the 13th of July 2004 and is still in operation at time of abstract writing. Digital photographies are taken every 4 hours, permitting so far at least one non-obstructed (rain, fog) picture per day. The first pictures in the series show an almost fully snow-covered glacier while the latest ones show bare ice up to the highest parts of the glacier. Snow is occasionally deposited during precipitation events but hardly last more than 3 days. Snow line position is deduced from pictures using a DEM with georeferenced points visible on pictures. It should then be compared with the modelled one. The automated photographic system provides not only snow cover to check snow/ice model results at seasonal time-scales, but also qualitative meteorological information (precipitation, cloud cover, fog) that may also help verify some aspects of the disaggregated meteorology in input of the model.
http://www-lgge.ujf-grenoble.fr/equipes/glaciers/DonneesDisp/ServiceObs/home.shtml
C43C-0239 1340h
NPEO North Pole Web Cams observe Arctic Summertime
In 2002, 2003, and 2004, North Pole Environmental Observatory (NPEO) automatic instrumented stations were deployed on an ice floe near the North Pole and started recording and telemetering data in April/May. The field teams also installed Web Cameras to show the installations and some scenery. These "web cams" collect and transmit images throughout the entire summer, from the beginning of snow melt to freeze-up in autumn and the onset of darkness. To appreciate the value of these data and images we should bear in mind that the proverbial "inaccessibility of the frozen Arctic Ocean" due to cold and darkness applies to the mild summer even more than to the cold and dark winter. The onset of melting usually occurs in early June, when the temperature reaches 0°C and the surface layer turns into a constant-temperature ice bath. In 2002, the temperature record shows an abrupt warming to about 0°C, on 24 May, suggesting an early arrival of the melt season. The warming event coincides with about a week of low short-wave (250 Wm-2) and high long-wave (300 Wm-2) down-welling radiation, which are typical of low overcast conditions. The web cam pictures of that period confirm the overcast. Both radiation and temperature values remained in the normal range for the rest of the summer, and freeze-up occurred as usual in the last week of August. Based on the early warming event in May, one may have expected an early onset of surface melting. Contrary to that expectation, the web cams show that it was not until late July 2002 when the snow cover took on a soggy appearance and isolated melt ponds appeared on the surface. For the rest of the summer, the web cam pictures show only insignificant melt pond coverage until the deposition of new snow in late August. The pictures clearly show that snow from the preceding winter survived the entire summer, and we must assume that there was no, or very little, ice ablation at the surface. In light of recent news about global warming and polar amplification, the all-summer snow cover of 2002 is clearly unexpected. Like the summer of 2002, the subsequent summer of 2003 also shows a somewhat belated (end of June) appearance of melt ponds but, by the first week of July, pond coverage was wide spread. Unexpectedly, toward the end of July, pond coverage decreased markedly while radiation and air temperatures were still at their normal summer values. A possible explanation is that the ice had become sufficiently porous for the melt water ponds to drain by percolation. However, in mid-August the melt ponds re-appeared putting in question the hypothetical pond drainage by percolation. The preceding samples illustrate the extraordinary value of the web cam pictures. The recently recorded data from automatic buoys and web cams represent a large, and very inexpensively obtained, increment of information about summer conditions in the central Arctic. The web cams have yielded interesting and sometimes puzzling information about summertime conditions. All data, whether they pertain to the atmosphere or the ocean or the ice, are valuable in their own right, and every additional year of observations during the summer represents a large addition to the existing data base.
http://www.arctic.noaa.gov/gallery_np.html
C43C-0240 1340h
Large and Small Scale Mapping of High Arctic Vegetation by NDVI: Thule, Greenland
An important component of arctic climate change is the assessment and quantification of vegetation cover. One method to assess this remotely is using the normalized difference vegetation index (NDVI), a relative measure of plant cover (greenness) of an area. NDVI values are often correlated with biomass figures and used to provide a spatial context for measurements of carbon flux, and potentially for estimating the spatially distributed response of carbon flux to climate change. Significant scaling issues arise when comparing NDVI values obtained on markedly different scales. When calculated at low resolution, such as 1 km AVHRR (Advanced Very High Resolution Radiometer) satellite images, NDVI results can vary significantly from higher resolution satellite images such as ASTER (Advanced Spaceborne Thermal Emission and Reflection) or ground measurements. Differences and similarities of NDVI values calculated from ASTER satellite images (15 meter pixels) are compared to those measured at a scale of 1 meter. Using a June 2003 ASTER satellite image, five sites were selected in the vicinity of the Thule Air Base as ground control plots representing five diverse classes of NDVI. These were photographed in the field during mid and late summer using a portable NDVI camera; NDVI values were calculated at one meter resolution. These data, along with coincident 2004 ASTER satellite images and vegetation transects will be used to better depict vegetation cover and to validate the satellite scale classes of vegetation for a typical High Arctic site in the Thule area. Preliminary results indicate that higher NDVI values from the satellite imagery do not always correspond to higher densities of vegetation, as presumed. Standing water and well-developed cryptogamic crusts may alter predicted results. Used on an annual basis, this method may be used to track changes in High Arctic vegetation cover and help to better understand the environmental changes occurring in the region.
C43C-0241 1340h
Video Observations of Anchor Ice/Sediment Interactions in Two Rocky Mountain Streams
Anchor ice is submerged ice that is attached or anchored to the bottom of rivers, lakes, and shallow seas. It forms in turbulent, supercooled water. In rivers, anchor ice usually forms at night and is released from the riverbed in the morning as the sun warms the water column. Released anchor ice often contains significant amounts of coarse-grained sediment. This entrained sediment can be transported (ice rafted) long distances downstream before it is released from the buoyant, floating ice back to the riverbed. Understanding sediment entrainment into anchor ice requires knowledge of the processes occurring at the sediment/ice interface. Viewing this interface through a freezing water column is a difficult task. Removing anchor ice from the water usually destroys the fragile contact between the ice and entrained sediment. In this study, we used an underwater video system to document anchor ice/sediment interactions in two small Rocky Mountain rivers. The video system allowed us to view: (1) the contact between attached anchor ice and the streambed; (2) the distribution of sediment in attached and released anchor ice masses; (3) the release of anchor ice from the bed; and (4) ice rafting of sediment in released anchor ice masses. One of the greatest benefits of the video system is the ability to see the in situ sediment distribution in attached and recently released anchor ice. Analysis of the video reveals that gravel concentrations are high on the top and bottom surfaces of anchor ice masses with relatively little gravel in the interior. The video system is not perfect for viewing ice underwater, however. The small difference between the refractive indices of ice and water makes it very difficult to discern ice crystal shapes and the exact nature of ice/sediment contacts. We are continuing to develop ways to enhance the image quality of ice crystals in water. Even with this shortcoming, the underwater video system is a very useful tool for observing in situ anchor ice/sediment relationships with minimal disturbance.