3 results for Adlam, Leah Seree

  • Temporal and spatial variation in active layer depth in the McMurdo Sound Region, Antarctica

    Adlam, Leah Seree; Balks, Megan R.; Seybold, Cathy A.; Campbell, David I. (2010)

    Journal article
    University of Waikato

    A soil climate monitoring network, consisting of seven automated weather stations, was established between 1999 and 2003, ranging from Minna Bluff to Granite Harbour and from near sea level to about 1700m on the edge of the polar plateau. Active layer depth was calculated for each site for eight successive summers from 1999/2000 to 2006/2007. The active layer depth varied from year to year and was deepest in the warm summer of 2001–02 at all recording sites. No trends of overall increase or decrease in active layer depth were evident across the up-to-eight years of data investigated. Average active layer depth decreased with increasing latitude from Granite Harbour (778S, active layer depth of.90 cm) to Minna Bluff (78.58S, active layer depth of 22 ± 0.4 cm), and decreased with increasing altitude from Marble Point (50m altitude, active layer depth of 49 ± 9 cm) through to Mount Fleming (1700m altitude, active layer depth of 6 ± 2 cm). When all data from the sites were grouped together and used to predict active layer depth the mean summer air temperature, mean winter air temperature, total summer solar radiation and mean summer wind speed explained 73% of the variation (R250.73).

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  • Permafrost thermal regime from two 30-m deep boreholes in southern victoria land, Antarctica

    Guglielmin, Mauro; Balks, Megan R.; Adlam, Leah Seree; Baio, Fabio (2011)

    Journal article
    University of Waikato

    Two 30-m deep permafrost temperature-monitoring boreholes were installed in bedrock, one at Marble Point and one in the Wright Valley, in the Ross Sea region of Antarctica. A soil climate-monitoring station in till is located near each borehole. The ground surface temperature (GST) was highly correlated with the air temperature at both sites in 2008. Thermal offsets were small (< 1 °C) in the till and negligible in the boreholes. The active layer was thicker in the boreholes than in the till, presumably because of the higher thermal diffusivity of the rock. The measured depth of zero annual temperature amplitude was around 27 m at Wright Valley and 25 m at Marble Point. Permafrost thickness was estimated at about 680 m at Wright Valley and 490 m at Marble Point. The GST history, reconstructed using an inversion procedure, suggests a slight cooling from 1998 to 2003 followed by a slight warming to 2008. Longer temperature records or deeper boreholes would be required to establish if long-term climate change has occurred.

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  • Soil climate and permafrost temperature monitoring in the McMurdo Sound region, Antarctica

    Adlam, Leah Seree (2009)

    Masters thesis
    University of Waikato

    A soil climate monitoring network, consisting of seven automated weather stations, was established between 1999 and 2003 in the McMurdo Sound region of Antarctica. Soil temperature, soil water content, air temperature, relative humidity, solar radiation, and wind speed and direction are recorded hourly and downloaded annually. Two 30 m deep permafrost temperature monitoring boreholes were established adjacent to the soil climate stations in the Wright Valley and at Marble Point in January 2007. Sixteen thermistors (accurate to ±0.1°C) were installed in each borehole measuring temperature once every hour and recording the mean every six hours. One year of permafrost temperatures were available (January 2007 to January 2008). The overall aim of this thesis was to make use of the soil climate monitoring database from 1999 to 2007 to investigate Antarctic soil climate. Active layer depth (depth of thawing) varied inter-annually, with no significant trend between 1999 and 2007. The active layer increased with decreasing latitude (R2 = 0.94), and decreased with increasing altitude (R2 = 0.95). A multiple regression model was produced whereby active layer depth was predicted as a function of mean summer air temperature, mean winter air temperature, total summer solar radiation and mean summer wind speed (R2 = 0.73). Annual temperature cycles were observed at all depths in the boreholes. At Marble Point, an annual temperature range of lt;1°C occurred at 15.2 m, lt;0.5°C at 18.4 m and lt;0.1°C at 26.4 m and at Wright Valley, an annual temperature range of lt;1°C occurred at 14.0 m, lt;0.5°C at 17.2 m and lt;0.1°C at 25.2 m. Given that the depth of Zero Annual Amplitude determined depends on the sensitivity of the measurement method, it is suggested that instead of referring to a depth of Zero Annual Amplitude , the depth at which the annual temperature range is less than a given value is a more useful concept. Mean annual and mean seasonal air and soil temperatures varied inter-annually and there was no significant trend of warming or cooling over the 1999 - 2007 period. Mean annual air temperatures were primarily influenced by winter air temperatures. Mean annual and mean summer soil temperatures were warmer than air temperatures due to heating by solar radiation. Mean summer air temperatures correlated well with the Southern Annular Mode Index (SAMI) at all sites (0.61 lt; R2 lt; 0.73) except Victoria Valley; however there was no correlation between mean annual or mean winter temperatures and the SAMI. Air temperature was linearly correlated with near-surface soil temperature (1.3 - 7.5 cm) (R2 gt; 0.79). Near-surface soil temperature was strongly correlated with incoming solar radiation at Victoria Valley (0.14 lt; R2 lt; 0.76) and Granite Harbour (0.49 lt; R2 lt; 0.82), but was not significantly correlated at other sites (0 lt; R2 lt; 0.57). There was no significant correlation between air temperature and wind speed, air temperature and solar radiation and near-surface soil temperature and wind speed, despite occasions of strong correlation on the diurnal time scale. Diurnal summer cycles in air and soil temperatures were driven by solar radiation. Multiple regressions combining the effects of air temperature, solar radiation and wind speed approximated near-surface soil temperatures well at every site during both summer and winter (0.88 lt; R2 lt; 0.98).

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