C11C-0514
Variability and Change in the Canadian Cryosphere: A Canadian Science Contribution to International Polar Year
The cryosphere (snow, permafrost and seasonally frozen ground, ice caps and glaciers, sea-, river-, and lake ice) represents a significant feature of the Canadian landscape that impacts climate, hydrology, the economy and the daily lives of all Canadians, especially those living in northern communities. Over the past few decades significant changes have been observed in cryospheric elements (e.g. decreases in snow cover, glacier extent, sea ice cover) that have been attributed to a warming climate. This poster presentation will highlight initial scientific results from the approved Canadian International Polar Year project "Variability and Change in the Canadian Cryosphere" that is being led by Environment Canada and involves 33 co- investigators from government, academia and the private sector and links with international collaborators. This project builds on Canadian strengths in remote sensing, climate analysis and modeling with the overall objective to observe and understand the current state of the cryosphere in Canada and determine how fast it is changing and why. Research activities are focused on: (1) developing new satellite-based capabilities to provide information on the current state of the Canadian cryosphere during the IPY period; (2) placing current cryospheric conditions in the context of the historical record to document the magnitude of changes over the 50 years since the last International Polar Year (IGY 1957-1958); (3) characterizing and explaining the observed variability and changes in the context of the coupled climate cryosphere system; and (4) improving the representation of the cryosphere in Canadian land surface and climate models to provide current and future climate simulations of the cryosphere for climate impact studies. The project also includes several outreach activities to engage northern communities in cryospheric monitoring and incorporate traditional knowledge with remotely-sensed information to generate new maps on local river ice and sea ice conditions to assist residents in planning safe navigation routes.
C11C-0515
Methylmercury distribution in the Upper Part of the Southern Ocean Water Column
Methylmercury has been determined in 93 sea water samples from the first thousand meters on 10 stations between Tasmania and Terre-Adelie in the Southern Ocean (SR3 Geotraces transect). Concentrations varied wildly from <15 to 858 fM, with a mean concentration of 272 fM and a standard deviation of 212 fM. The vertical distributions exhibited systematic nutrient like profiles. Highest methylmercury concentrations were found in the high productive region near the Antarctica divergence zone and the lowest in and quite unproductive pool of water north of the Subantarctic Front structure.
C11C-0516
Recent Mapping and Sampling on Chukchi Borderland and the Alpha/Mendeleev Ridge Complex
Since 2003, four cruises on the icebreaker USCG HEALY have collected high-resolution multibeam sonar
mapping data in the Amerasia Basin in support of a potential submission by the U.S. for an extended
continental shelf as defined under the United Nations Convention on Law of the Sea Article 76. The latest of
these cruises (HEALY0805), completed in early Sept.of 2008, extended this mapping to the southern portions
of the Alpha/Mendeleev Ridge complex, and supplemented the mapping with seven dredge stations,
providing rare, direct sampling of both regions. While sparse in comparison to complete-coverage
multibeam sonar surveys (due to the difficulties associated with operating in ice-covered waters), the new
multibeam sonar data still provide an unprecedented new view of the tectonic, sedimentary, glacial and fluid-
flow related processes in the Arctic Ocean.
The Chukchi Borderland is characterized by shallow plateaus that often show evidence of interaction with
icebergs and glaciers (scours and grooves) at depths as great as 900 m, as well as the presence of
numerous gas/fluid expulsion features (pockmarks and acoustic wipe-out zones). The topographic highs
associated with the Borderland are often bounded by very steep scarps including the eastern edge of
Northwind Ridge (the Northwind Escarpment) which is a 600 km long NNE trending feature with an average
slope of 10-15 degrees. Similar steep-sided ridges, separated by deep linear valleys also appear in mapped
areas of the Alpha/Mendeleev Ridge complex. Some of these features have slopes as great at 60 degrees
and thus are excellent targets for dredging. Our dredging of these slopes has returned a wide array of
volcanic and sedimentary rock types, many of which appear to be representative of outcrops (rather than ice
rafted material). A preliminary shipboard examination of these samples (they were just collected this morning
– 3 September 2008 – a few days before the abstract is due) shows them to include mudstone, sandstone,
shale, breccia, along with volcanic and metamorphic rocks lending support to the earlier evidence for the
continental origin of the Chukchi Borderland. Dredges from the topographic highs of the southern part of
Alpha/Mendeleev Ridge complex returned indurated sediment with defined sedimentary structures that
appear to be non-marine in origin; further descriptions of the nature of these rocks and speculation about
their implications for the origin of the features from which they were dredged will require more detailed
laboratory analyses which will be carried out in the coming months.
http://www.ccom.unh.edu
C11C-0517
The Role of Albedo as a Forcing in the Formation and Development of Melt Ponds on Undeformed First Year Sea Ice
Melt pond formation on first year sea ice is strongly influenced by the pre-melt morphological properties of the snow and ice cover. The complex process of melt pond development on first-year sea ice greatly reduces its albedo, increasing the solar energy input and melt rate of underlying ice. Areas with optically thin snow covers have smaller albedos. Observations and energy flux calculations suggest that this results in greater melting of thin snow areas and underlying ice early in the season. Thin snow areas on undeformed first year ice are thus predisposed for initial melt pond formation. Time series photography, depth measurements, and Light Detection and Ranging (LiDAR) measurements tracking the evolution of melt ponds near Barrow, AK show strong correlation between the locations where melt ponds first form and where they can be found late in the season, suggesting the presence of a feedback process maintaining pond location. Albedo transect measurements and energy budget calculations show that morphological features which have low albedo, such surface water and sediment, are key to maintaining the location of the melt ponds by increasing energy flux into them. Combined with studies regarding the effects of ice topography and atmospheric forcing on pond formation, the observations of this study could enable prediction of melt pond and albedo progression based on early season indicators. This in turn could allow energy forcing estimates and melt predictions in the seasonal ice zone.
C11C-0518
Extreme melt-freeze processes on Antarctic sea ice: implications for evolution of perennial ice mass balance and biological communities
The evolution of Antarctic perennial sea ice is dominated by processes associated with its thick snow cover. The key processes (snow ice formation via seawater inundation and freezing and superimposed ice formation via meltwater percolation and refreezing) are distinct from those that dominate in the Arctic and are not adequately described in models. We present sea ice core data obtained in the Bellingshausen Sea in late summer, 2007. Evidence for extreme melt and refreezing of the snow cover was found in the eastern Bellingshausen Sea with as much as two meters or more of the snowpack converted into sea ice per year – far greater than has been observed before. In the western Bellingshausen, snow ice formation dominated the surface mass balance, presumably due to colder conditions and deeper snow cover. In contrast to previous observations, we find evidence for refreezing of snow meltwater in ice types other than classic superimposed ice. This hinders the unambiguous identification of ice types and may have implications for previously reported mass balance data. Highly productive gap-layer communities were widespread in the western Bellingshausen where snow ice was more prevalent, while they were less common in the warmer east where superimposed ice dominated. To examine these processes the ice core data are compared with results of a complex thermodynamic-hydraulic model. Based on these results we hypothesize that the snow cover and melt play an important role in structuring biological communities. Warmer conditions may lead to extreme meltwater percolation and refreezing that, while stabilizing the ice cover, inhibits the formation of porous gaps and limits sea ice primary productivity. We also describe plans for two research cruises in early 2009 where we will further investigate these phenomena.
C11C-0519
Permafrost and Active Layer Monitoring in the Maritime Antarctic: A Contribution to TSP and ANTPAS projects
Permafrost and active layer monitoring in the Maritime Antarctic (PERMANTAR) is a Portuguese funded International Project that, in cooperation with the Spanish project PERMAMODEL, will assure the installation and the maintenance of a network of boreholes and active layer monitoring sites, in order to characterize the spatial distribution of the physical and thermal properties of permafrost, as well as the periglacial processes in Livingston and Deception Islands (South Shetlands). The project is part of the International Permafrost Association IPY projects Thermal State of Permafrost (TSP) and Antarctic and Sub-Antarctic Permafrost, Soils and Periglacial Environments (ANTPAS). It contributes to GTN-P and CALM-S networks. The PERMANTAR-PERMAMODEL permafrost and active layer monitoring network includes several boreholes: Reina Sofia hill (since 2000, 1.1m), Incinerador (2000, 2.3m), Ohridski 1 (2008, 5m), Ohridski 2 (2008, 6m), Gulbenkian-Permamodel 1 (2008, 25m) and Gulbenkian- Permamodel 2 (2008, 15m). For active layer monitoring, several CALM-S sites have been installed: Crater Lake (2006), Collado Ramos (2007), Reina Sofia (2007) and Ohridski (2007). The monitoring activities are accompanied by detailed geomorphological mapping in order to identify and map the geomorphic processes related to permafrost or active layer dynamics. Sites will be installed in early 2009 for monitoring rates of geomorphological activity in relation to climate change (e.g. solifluction, rockglaciers, thermokarst). In order to analyse the spatial distribution of permafrost and its ice content, electrical resistivity tomography (ERT), and seismic refraction surveys have been performed and, in early 2009, continuous ERT surveying instrumentation will be installed for monitoring active layer evolution. The paper presents a synthesis of the activities, as well as the results obtained up to the present, mainly relating to ground temperature monitoring and from permafrost characteristics and spatial distribution.
C11C-0520
Nares Strait Freshwater Flux From a Three-Year Moored Array
Nares Strait is a 40-km wide and 500-km long channel to the west of Greenland that facilitates the exchange
of heat and freshwater between the Arctic and Atlantic Oceans. The Canadian Archipelago Throughflow
Study and its ongoing International Polar Year extension focus on the dynamics in Nares Strait for the
2003/06 and 2007/09 periods, respectively. A moored array measures currents, temperature, conductivity,
ice thickness and subsurface pressure near 80.5° N, and resolves the internal Rossby radius of
deformation.
We concentrate on variations in salinity and density across the section as a function of time and calculate
geostrophic velocities, transports, and fluxes. The time-mean geostrophic velocity section shows a surface-
intensified 25 cm/s southward flow adjacent to the western side of the strait and a weak 5 cm/s northward flow
on the opposite side of the channel adjacent to Greenland. Salinity variations of about 2 psu relate to the
freshwater outflow from the Arctic Ocean. A preliminary estimate of the geostrophic freshwater flux through
Nares Strait is 48 ± 5 mSv (103 m3/s). This three-year mean estimate compares to about 30
mSv from earlier ADCP observations in the strait. We investigate across and along-channel pressure
gradients forcing.
http://newark.cms.udel.edu/~cats/
C11C-0521
Regional Shoreline Change Along the North Slope of Alaska
Climate change impacts to the north coast of Alaska threaten sensitive ecosystems, critical energy-related infrastructure, native Alaskan housing and traditional lifestyles, trust species and their habitats, and large tracts of Federally-managed land. Although there are several site-specific and limited regional studies documenting coastal change along the Beaufort and Chukchi Sea coasts, no comprehensive study has documented coastal change or evaluated its causes on a regional scale. As part of a National Assessment of Shoreline Change study along open-ocean sandy shores of the United States, the U.S. Geological Survey is evaluating shoreline changes along the north slope coast of Alaska between Peard Bay and the Canadian border. Rates of change will be calculated for both the mainland and barrier island coasts using shorelines derived from circa 1947 and 1987 NOS T-sheets and from orthorectified photography and/or satellite imagery collected between 2000 and 2007. Here we present results from the first phase of the study, Colville River to Pt. Thomson, for three time periods (1947, 1987, 2004-7). In contrast to previous independent studies, which have documented localized erosion rates of up to 16 m/yr along portions of Alaska's north slope, results from this study show that on a regional scale, shoreline erosion rates along the mainland coast are typically less than 2 m/yr. The offshore barrier islands, however, are highly dynamic and show high rates of localized shoreline retreat along with a regionally consistent decrease in overall land area and associated rotation and migration to the southwest since the 1940s. As part of this study, continued data collection, analysis, and numerical and analytical modeling of the coast and nearshore environments will provide much needed data sets from which to evaluate future changes along this stretch of coast in response to sea-level rise, variability in the Arctic summer sea-ice extent, increased storminess, and other possible effects of global climate change.
C11C-0522
Strength of Frozen Soils and Tundra Travel Criteria
Energy development on the North Slope of Alaska (an area of very limited roads) is dependent on winter exploration activities. The sensitive tundra environment dictates that most exploration takes place in the middle of winter, when snow cover and frozen soil conditions allow tundra traffic without adverse damage to the Arctic landscape. The current management protocols do not take into account the range of soil conditions and frozen ground characteristics. Management criteria require soils at 30 cm depth to be below - 5°C. Since establishment of this criteria, a number of meteorological and geotechnical data stations have been established on the North Slope. Soil temperature and unfrozen soil-moisture content data from a dozen monitoring stations in northern Alaska were examined along with laboratory determined temperature- and water-dependent soil strength values from the literature in order to estimate soil strength in the field as the soil temperature falls below freezing. Soil strength at temperature below 0°C depends on soil composition, salinity, and unfrozen water content. In general, bearing capacity of soils without salt changes sufficiently in the range of temperature from 0 to -1°C and very gradually with lower temperature. Soil composition and ice content are very important strength factors. The goal is to maximize permissible tundra travel time while minimizing environmental damage. If tundra travel restrictions, currently based on temperature and snow depth, would allow travel at slightly higher soil temperatures (and slightly higher soil water contents), the length of the tundra travel season could be increased, resulting in considerable economic benefit while maintaining environmental quality.
C11C-0523
Analysis of Organic Carbon in Arctic Shelf Sediments
The Arctic environment is extremely sensitive to changes in climate and the effects of these changes have global scale implications. One element of the Arctic that needs careful study is the organic carbon cycle. With that goal in mind, we examined sediments from 14 cores collected on the shelves of the Bering, Chukchi, and Beaufort Seas during a cruise on July 2007 aboard the CCGS Sir Wilfrid Laurier. The samples were subjected to a variety of geochemical analyses including elemental analysis for carbon and nitrogen, surface area analysis and stable carbon and nitrogen isotopes. Our primary objective was to to quantify the amount of organic carbon preserved in these sediments and determine the relative contributions of allochthonous and autochthonous sources to the organic matter deposited in these different Arctic margins. The cores were found to be extremely variable, with organic carbon content varying between 0.3% and nearly 6.0%, and variations on a similar scale in total nitrogen content. The cores were characterized by a large range of stable isotopic signatures, from essentially purely marine input to strong terrestrial signals. There was also significant variation among depositional horizons within individual cores, particularly in the stable isotope measurements. Lastly, mixing models based on the stable isotope measurements were utilized in an attempt to quantify the actual contributions of marine and terrestrial organic matter.
C11C-0524
Twenty year record of vegetation change from long-term plots in Alaskan tundra
We examined change in plant species composition at two sites in the Southern Alaska Foothills, on the north slope of the Brooks Range, over a 20-year period. Current models and experimental work with tundra vegetation have predicted an increase in shrub species and a decrease in graminoid species as a response to climatic warming. Furthermore, the warming of the Alaskan Arctic during the past 150 years has accelerated over the last three decades and is expected to increase vegetation productivity in tundra if shrubs become more abundant. Decadal change in vegetation in tundra landscapes may be both subtle and slow. Interpreting such change is complicated by spatial variation at small scales and by difficulty in understanding how point changes in species composition relate to landscape-level change in vegetation. Our approach involved resampling the same points in a series of permanent plots over a multi-year interval, using large sample sizes, and analyzing several aspects of compositional change. Our analysis was designed to look at changes in overall species' abundance over time and at relationships between species in terms of the likelihood of one species replacing another. Understanding relationships between species increases the predictive power of measures of species composition and abundance in a time series. We found significant increases in abundance of specific shrub and graminoid species, and a general increase in the extent of the canopy, with a concurrent decrease in the abundance of understory mosses. These changes, extrapolated over the broad expanse of similar vegetation in the Arctic, may have profound above and below ground effects including changes in soil properties, carbon storage and nutrient cycling, and plant community composition.