Past climate changes and permafrost depth at the Lake El'gygytgyn site: implications from data and thermal modeling 1Geophysica Beratungsgesellschaft mbH, Aachen, Germany
22 Jan 2013
2Alfred Wegener Institute for Polar and Marine Research, Potsdam, Germany
3Department of Earth Sciences, Astronomy and Astrophysics, Faculty of Physical Sciences, Universidad Complutense de Madrid, Madrid, Spain
Received: 06 July 2012 – Published in Clim. Past Discuss.: 16 July 2012 Abstract. This study focuses on the temperature field observed in boreholes drilled as part of interdisciplinary
scientific campaign targeting the El'gygytgyn Crater Lake in NE Russia. Temperature data are available
from two sites: the lake borehole 5011-1 located near the center of the lake reaching 400 m
depth, and the land borehole 5011-3 at the rim of the lake, with a depth of 140 m. Constraints on
permafrost depth and past climate changes are derived from numerical simulation of the
thermal regime associated with the lake-related talik structure. The thermal properties of the subsurface
needed for these simulations are based on laboratory measurements of representative cores from the
quaternary sediments and the underlying impact-affected rock, complemented by further
information from geophysical logs and data from published literature.
Revised: 12 December 2012 – Accepted: 13 December 2012 – Published: 22 January 2013
The temperature observations in the lake borehole 5011-1 are dominated by thermal perturbations related to
the drilling process, and thus only give reliable values for the lowermost value in the borehole. Undisturbed
temperature data recorded over more than two years are available in the 140 m deep land-based borehole
5011-3. The analysis of these observations allows determination of not only the recent mean annual ground
surface temperature, but also the ground surface temperature history, though with large uncertainties.
Although the depth of this borehole is by far too insufficient for a complete
reconstruction of past temperatures back to the Last Glacial Maximum, it still affects
the thermal regime, and thus permafrost depth. This effect is constrained by numerical
modeling: assuming that the lake borehole observations are hardly influenced by the past
changes in surface air temperature, an estimate of steady-state conditions is possible,
leading to a meaningful value of 14 ± 5 K for the post-glacial warming. The strong
curvature of the temperature data in shallower depths around 60 m can be explained by a
comparatively large amplitude of the Little Ice Age (up to 4 K), with low temperatures
prevailing far into the 20th century. Other mechanisms, like varying porosity, may also
have an influence on the temperature profile, however, our modeling studies imply a major
contribution from recent climate changes.
Citation: Mottaghy, D., Schwamborn, G., and Rath, V.: Past climate changes and permafrost depth at the Lake El'gygytgyn site: implications from data and thermal modeling, Clim. Past, 9, 119-133, doi:10.5194/cp-9-119-2013, 2013.