11:15 〜 11:30
[ACG43-09] グリーンランド北西部カナック氷帽における2012–2021年の表面質量収支変動
キーワード：グリーンランド、氷河、氷帽、表面質量収支、カナック
Mass loss of peripheral glaciers and ice caps in Greenland accounts for 13 % of the global glacier mass loss from 2000 and 2019 (IPCC, 2021), which forms a substantial contribution to global sea level rise. The mass loss is spreading from southern to northern Greenland (Kjær et al., 2012). However, details of the spatial and temporal variability remain unclear because only a few in-situ glacier studies have been reported in northern Greenland. To fill the gap of our knowledge, we have conducted surface mass balance measurement on Qaanaaq Glacier, an outlet glacier of Qaanaaq Ice Cap in northwestern Greenland since 2012 (Sugiyama et al., 2014). In this study, we utilized nine-year-long field data to quantify the mass change of the entire Qaanaaq Ice Cap from 2012 to 2021. We discuss the results with meteorological data collected on the ice cap at 944 m a.s.l. (SIGMA-B) (Aoki et al., 2014).
Surface mass balance of the glacier was observed by installing aluminum poles at six locations situated at 243–968 m a.s.l.. The height of the pole above ice or snow surface was measured every year in August to obtain annual mass balance. Snow density was measured when glacier surface was covered with snow. The results from 2012 to 2021 show mean values of 0.20 m w.e. a−1 at 968 m a.s.l. and −1.68 m w.e. a−1 at 243 m a.s.l. with interannual variability of ~2 m w.e. a−1. Mass balance at 427m a.s.l. showed generally more negative than those expected from its dependence on elevation, suggesting significant melting due to ice surface darkening in the region (Sugiyama et al., 2014). According to recent study, the darkening is influenced by insoluble particles accumulated during Holocene Thermal Maximum and advected from higher ablation zone (Matoba et al., 2020).
Mass balance over the entire ice cap was computed for each year, by assuming that surface mass balance is a function of elevation. As the result, The mean specific mass balance of the ice cap from 2012 to 2021 was −3.38 ± 0.21 m w.e.. The most negative mass balance was observed in 2014/15 (−1.08 ± 0.04 m w.e. a−1) and 2019/20 (−0.91 ± 0.01 m w.e. a−1). We attribute these results to relatively large number of positive degree days and relatively small accumulation (208 ℃ day and 0.32 m w.e. a−1 in 2014/15 and 244 ℃ day and 0.48 m w.e. a−1 in 2019/20 at 944 m a.s. l.). The ice cap gained mass only in 2017/18 (0.24 ± 0.01 m w.e. a−1), when a relatively small number of positive degree days was recorded (48 ℃ day at 944 m a.s.l.).
Our results imply rapid mass loss of the glaciers and ice caps in the Qaanaaq region over the last 9 years under the influence of warming climate. Nevertheless, significantly large spatial and temporal variability was observed in the rate of the mass loss. Continuous effort of in-situ measurement and data analysis are required to understand the mass loss of the glaciers in the region and its driving mechanism.
Reference:
Aoki et al. (2014). Field activities of the “snow impurity and glacial microbe effects on abrupt warming in the Arctic” (SIGMA) project in Greenland in 2011–2013. Bulletin of Glaciological Research, 32, 3–20.
IPCC (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, In Press.
Kjær et al. (2012). Aerial photographs reveal late-20th-century dynamic ice loss in northwestern Greenland. Science, 337 (6094), 569–573.
Matoba, et al. (2020). Spatial Distribution of the Input of Insoluble Particles Into the Surface of the Qaanaaq Glacier, Northwestern Greenland. Frontiers in Earth Science, 8.
Sugiyama et al. (2014). Initial field observation on Qaanaaq ice cap, northwestern Greenland. Annals of Glaciology, 55(66), 25–33
Surface mass balance of the glacier was observed by installing aluminum poles at six locations situated at 243–968 m a.s.l.. The height of the pole above ice or snow surface was measured every year in August to obtain annual mass balance. Snow density was measured when glacier surface was covered with snow. The results from 2012 to 2021 show mean values of 0.20 m w.e. a−1 at 968 m a.s.l. and −1.68 m w.e. a−1 at 243 m a.s.l. with interannual variability of ~2 m w.e. a−1. Mass balance at 427m a.s.l. showed generally more negative than those expected from its dependence on elevation, suggesting significant melting due to ice surface darkening in the region (Sugiyama et al., 2014). According to recent study, the darkening is influenced by insoluble particles accumulated during Holocene Thermal Maximum and advected from higher ablation zone (Matoba et al., 2020).
Mass balance over the entire ice cap was computed for each year, by assuming that surface mass balance is a function of elevation. As the result, The mean specific mass balance of the ice cap from 2012 to 2021 was −3.38 ± 0.21 m w.e.. The most negative mass balance was observed in 2014/15 (−1.08 ± 0.04 m w.e. a−1) and 2019/20 (−0.91 ± 0.01 m w.e. a−1). We attribute these results to relatively large number of positive degree days and relatively small accumulation (208 ℃ day and 0.32 m w.e. a−1 in 2014/15 and 244 ℃ day and 0.48 m w.e. a−1 in 2019/20 at 944 m a.s. l.). The ice cap gained mass only in 2017/18 (0.24 ± 0.01 m w.e. a−1), when a relatively small number of positive degree days was recorded (48 ℃ day at 944 m a.s.l.).
Our results imply rapid mass loss of the glaciers and ice caps in the Qaanaaq region over the last 9 years under the influence of warming climate. Nevertheless, significantly large spatial and temporal variability was observed in the rate of the mass loss. Continuous effort of in-situ measurement and data analysis are required to understand the mass loss of the glaciers in the region and its driving mechanism.
Reference:
Aoki et al. (2014). Field activities of the “snow impurity and glacial microbe effects on abrupt warming in the Arctic” (SIGMA) project in Greenland in 2011–2013. Bulletin of Glaciological Research, 32, 3–20.
IPCC (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, In Press.
Kjær et al. (2012). Aerial photographs reveal late-20th-century dynamic ice loss in northwestern Greenland. Science, 337 (6094), 569–573.
Matoba, et al. (2020). Spatial Distribution of the Input of Insoluble Particles Into the Surface of the Qaanaaq Glacier, Northwestern Greenland. Frontiers in Earth Science, 8.
Sugiyama et al. (2014). Initial field observation on Qaanaaq ice cap, northwestern Greenland. Annals of Glaciology, 55(66), 25–33