Cathy Connor

Submarine melting at the terminus of a temperate tidewater glacier, LeConte Glacier, Alaska, U.S.A.

Abstract Heat, fresh- and sea-water balances indicate that the late-summer rate of submarine melting at the terminus of tidewater LeConte Glacier, Alaska, U.S.A., in 2000 was about 12 m d−1 w.e., averaged over the submerged face. This is 57% of the estimated total ice loss at the terminus (calving plus melting) at this time. Submarine melting may thus provide a significant contribution to the overall ablation of a tidewater glacier. Oceanographic measurements (conductivity–temperature–depth) made 200–500m from the terminus identified an isohaline (27 ppt) and isothermal (7.2°C) layer extending from 130 m depth to the fjord floor. Capping this is a 40 m thick overflow plume, distinguished by high outflow rates, low salinity (22–25 ppt) and lower temperatures (5–6°C). Mixing models indicate that fresh water comprised about 11% of this plume; it originates mostly as subglacial discharge whose buoyancy drives convection at the terminus. Deep, warm saline waters are incorporated into the plume as it ascends, causing substantial melting of ice along the submarine face. The calving terminus undergoes seasonal changes that coincide with changes in subglacial discharge and fjord water temperatures, and we suggest that these fluctuations in terminus position are directly related to changes in submarine melting.

Twentieth century thinning of Mendenhall Glacier, Alaska, and its relationship to climate, lake calving, and glacier run-off

Mendenhall Glacier is a dynamic maritime glacier in southeast Alaska that is undergoing substantial recession and thinning. The terminus has retreated 3 km during the 20th century and the lower part of the glacier has thinned 200 m or more since 1909. Glacier-wide volume loss between 1948 and 2000 is estimated at 5.5 km 3 . Wastage has been the strongest in the glacier’s lower reaches, but the glacier has also thinned at higher elevations. The shrinkage of Mendenhall Glacier appears to be due primarily to surface melting and secondarily to lake calving. The change in the average rate of thinning on the lower glacier, 2 m a � 1 since 1982, agrees qualitatively with observed warming trends in the region. Mean annual temperatures in Juneau decreased slightly from 1947 to 1976; they then began to increase, leading to an overall warming of f1.6 jC since 1943. Lake calving losses have periodically been a small but significant fraction of glacier ablation. The portion of the terminus that ends in the lake is becoming increasingly vulnerable to calving because of a deep pro-glacial lake basin. If current climatic trends persist, the glacier will continue to shrink and the terminus will recede onto land at a position about 500 m inland within one to two decades. The glacier and the meltwaters that flow from it are integral components of the Mendenhall Valley hydrologic system. Approximately 13% of the recent average annual discharge of the Mendenhall River is attributable to glacier shrinkage. Glacier melt contributes 50% of the total river discharge in summer. D 2002 Elsevier Science B.V. All rights reserved.

The Neoglacial landscape and human history of Glacier Bay, Glacier Bay National Park and Preserve, southeast Alaska, USA:

The Neoglacial landscape of the Huna Tlingit homeland in Glacier Bay is recreated through new interpretations of the lower Bays fjordal geomorphology, late Quaternary geology and its ethnographic landscape. Geological interpretation is enhanced by 38 radiocarbon dates compiled from published and unpublished sources, as well as 15 newly dated samples. Neoglacial changes in ice positions, outwash and lake extents are reconstructed for c. 5500—200 cal. yr ago, and portrayed as a set of three landscapes at 1600—1000, 500—300 and 300—200 cal. yr ago. This history reveals episodic ice advance towards the Bay mouth, transforming it from a fjordal seascape into a terrestrial environment dominated by glacier outwash sediments and ice-marginal lake features. This extensive outwash plain was building in lower Glacier Bay by at least 1600 cal. yr ago, and had filled the lower bay by 500 cal. yr ago. The geologic landscape evokes the human-described landscape found in the ethnographic literature. Neoglacial climate and landscape dynamism created difficult but endurable environmental conditions for the Huna Tlingit people living there. Choosing to cope with environmental hardship was perhaps preferable to the more severely deteriorating conditions outside of the Bay as well as conflicts with competing groups. The central portion of the outwash plain persisted until it was overridden by ice moving into Icy Strait between AD 1724—1794. This final ice advance was very abrupt after a prolonged still-stand, evicting the Huna Tlingit from their Glacier Bay homeland.

SEAMONSTER: A demonstration sensor web operating in virtual globes

A sensor web is a collection of heterogeneous sensors which autonomously reacts to the observed environment. The SouthEast Alaska MOnitoring Network for Science, Technology, Education, and Research (SEAMONSTER) project has implemented a sensor web in partially glaciated watersheds near Juneau, Alaska, on the edge of the Juneau Icefield. By coupling the SEAMONSTER sensor web with digital earth technologies the scientific utility, education and public outreach efforts, and sensor web management of the project all greatly benefit. This paper describes the scientific motivation for a sensor web, the technology developed to implement the sensor web, the software developed to couple the sensor web with digital earth technologies, and demonstrates the SEAMONSTER sensor web in a digital earth framework.

Experiential Discoveries in Geoscience Education: The EDGE Program in Alaska

Alaskas students directly observe their high-latitude landscape changing in response to both active tectonics and warming temperatures. Alaskas secondary school teachers must increasingly provide Earth systems science education that integrates these personal observations with geospatial datasets and satellite images using Geographic Information System (GIS) technology. Alaskan job opportunities requiring Earth science and GIS training are increasing, yet less than 1% of Alaskas university students choose geoscience-related majors. The EDGE (Experiential Discoveries in Geoscience Education) program provides a year of Earth science college courses, geologic field experiences, GIS instruction, and technical support for groups of Alaskan high and middle school teachers and their students. Since 2005 EDGE has increased the Earth science content knowledge and GIS and computer skills of 34 Alaskan teachers and facilitated the transfer of their knowledge and skills into Alaskas science classrooms. More than 500 middle school students have learned GIS from EDGE teachers and 30 EDGE high school students have conducted original research utilizing GIS related to landscape change and its impacts on their own communities. Long-term EDGE goals include improving student performance on the newly implemented (2007) 10th grade standards-based science test scores, recruiting first-generation college students, and increasing the number of Earth science majors in the University of Alaska system. More information on EDGE programs is available at .

Sensor Webs in Digital Earth: Monitoring Climate Change Impacts

The University of Alaska Southeast is currently implementing a sensor web identified as the SouthEast Alaska MOnitoring Network for Science, Telecommunications, Education, and Research (SEAMONSTER). From power systems and instrumentation through data management, visualization, education, and public outreach, SEAMONSTER is designed with modularity in mind. We are utilizing virtual earth infrastructures to enhance both sensor web management and data access. We will describe how the design philosophy of using open, modular components contributes to the exploration of different virtual earth environments. We will also describe the sensor web physical implementation and how the many components have corresponding virtual earth representations. This presentation will provide an example of the integration of sensor webs into a digital earth. We suggest that sensor networks and sensor webs should integrate into digital earth systems and provide a resource easily accessible to both scientists and the public. The initial scientific application of the SEAMONSTER sensor web is to monitor climate change impacts of glaciated watersheds in Southeast Alaska. Melting glaciers are dominating the biogeochemistry of watersheds and as the glaciers disappear, this influence will diminish. By monitoring these watersheds using a sensor web, we are improving knowledge regarding impacts of climate change.