Autonomous ice sheet surface mass balance measurements from cosmic rays
Observations of mass accumulation and net balance on glaciers and ice sheets are sparse due to the difficulty of acquiring manual measurements and the lack of a reliable remote-sensing method. The methodology for recording the water-equivalent accumulation of snowfall using the attenuation of fa...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-06-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/12/2099/2018/tc-12-2099-2018.pdf |
| Summary: | Observations of mass accumulation and net balance on glaciers
and ice sheets are sparse due to the difficulty of acquiring manual
measurements and the lack of a reliable remote-sensing method. The
methodology for recording the water-equivalent accumulation of snowfall using
the attenuation of fast neutrons generated by cosmic ray impacts was
developed in the 1970s and has been employed in large-network snowpack
monitoring but has yet to be applied to glaciers and ice sheets. In order to
assess this potential method, we installed a cosmic ray neutron-sensing
device at Summit Camp, Greenland, in April 2016. Hourly neutron count was
recorded for ∼ 24 months and converted to water-equivalent thickness
after correcting for variability in atmospheric pressure and incoming cosmic
radiation. The daily accumulation estimates are analysed for noise level and
compared to manual surface core and snow stake network measurements. Based on
measurements of up to 56 cm of water equivalent, we estimate the sensor's
precision to be better than 1 mm for water-equivalent thicknesses less than
14 cm and better than 1 cm in up to 140 cm, or approximately 0.7 %.
Our observations agree with the surface core measurements to within their
respective errors, with temporary biases that are explained by snow drifting,
as supported by comparison to the snow stake network. Our observations reveal
large temporal variability in accumulation on daily to monthly scales, but
with similar annual totals. Based on these results, cosmic ray sensing
represents a potentially transformative method for acquiring continuous in
situ measurements of mass accumulation that may add constraint to glacier and
ice sheet mass balance estimates from meteorological models and remote
sensing. |
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| ISSN: | 1994-0416 1994-0424 |