New contribution from Frédéric Bouchard et al. on greenhouse gases emitted from fresh water ecosystems in the high Arctic

July 27, 2015 in Article, Paper

Glacial lake sediments: nice paleoenvironmental archives.

May 25, 2015 in @en, focus-en

Fig1-map

Figure 1: Location and context around kettle lake ‘BYL36’. The lake, containing sediments dated at 10.8 ka BP, is located just to the north-east (slightly upstream) of a terminal moraine dated at 9.8 ka BP (photos: V. Preskienis [upper] et GeoEye-1 [lower]).

The Holocene history of glacier valleys on Bylot Island, since the last glaciation, has been reconstructed by carefully studying the landscape features. For example, in the valley of glacier C-79 (map, Figure 1), the maximum advance of the glacier was dated at 9860 ± 140 BP (before present), and it was suggested that the glacier front was in contact with shallow marine waters (Allard, 1996). This interpretation is based on mollusc shells found in marine clay and dated using the radiocarbon (14C) technique, which would give a ‘calibrated’ age of 11 440 ± 380 cal BP.

 

During the summer of 2014, Geocryolab members used a novel method of bathymetric mapping in order to characterize the morphology of a glacial lake located in the valley (see other post about the sonar-GPS system). It is a kettle lake, formed by the melting of ground ice buried in soil after glacier retreat, and located near the position of the glacier front mentioned above (Fig1). A > 30-cm long sediment core (Fig2) was collected from the deepest part of the lake (~ 12 m), and 14C dating at the base of these lacustrine sediments gave an age of 10 825 ± 45 BP, or 12 730 ± 50 cal BP once calibrated. The exact nature of these sediments still has to be confirmed, but this shows the great potential of studying sedimentary archives contained in lakes. Which makes our friend ‘Zodiac Sherpa’ (Fig3) very optimistic.

Fig2 Sediment core

Figure 2: Sediment core collected from the deepest part (~ 12 m) of kettle lake ‘BYL36’ (photo: F. Bouchard).

Fig3 Sediment Coring Sherpa

Figure 3 : Motivated young researcher who wisely checks, before jumping to the next coring site with a zodiac on his back, if he has all the equipment he needs. We can see the percussion corer just behind him (photo: V. Preskienis).

 

 

 

 

 

 

 

 

 

 

For further information:

Allard, M. (1996) : Geomorphological changes and permafrost dynamics: Key factors in changing arctic ecosystems. An example from Bylot Island, Nunavut, Canada. Geoscience Canada, 23, 205-212.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Ultra-rapid bathymetric mapping: a very useful technique in paleolimnological research

March 25, 2015 in Article

Author: Frédéric Bouchard

The Geocryolab has recently acquired a simple, efficient and affordable lake bottom mapping system. The system consists of a portable echo-sounder (‘sonar’) equipped with a GPS, similar to those used by recreational fishermen for spotting fish shoals (Fig1, A ). The sonar can be installed quickly and simply in a small boat (zodiac) using plumbing pieces, Duct Tape and a bit of ingenuity (Fig1, B). Mapping surveys involve moving on lake surfaces along navigation lines while continuously recording water depths (Fig1, C). A separate software then allows to interpolate water depths between navigation lines in order to generate a high resolution bathymetric map (Fig1, D).

This technique was successfully tested in July 2014 on Bylot Island, Nunavut. In the context of our research in paleolimnology (history of ponds and lakes studying lacustrine sediment properties), this technique appeared very useful, if not crucial, for identifying the best location to sample lake sediment cores (generally, the deepest location within the lake). Moreover, as an important logistical advantage, the whole ‘kit’, including a small zodiac, can be deployed and used in the field by only one person, nicknamed the ‘Zodiac Sherpa’ (Fig1, E).

For further information: Bouchard et al., submitted (GEOQuebec2015 abstract, to be confirmed).

Figure_capsule1

Figure 1 : A) Geocryolab’s portable sonar, which allows to continuously record lake bottom depths. Model 859XD with integrated GPS from Humminbird (photo: F. Bouchard); B) Sonar installation in a small zodiac. Sonar antenna is fixed outside the zodiac to stay on the water surface during navigation (photo: F. Bouchard); C) Navigation lines surveyed with the sonar. Depths are indicated by the color range; D) Bathymetric map generated from the navigation lines. We can see a deeper ‘trench’ (10-m depth), non visible from aerial photographs or other field surveys, which allows to quickly identify the best coring site; E) Motivated young researcher who carries, all by himself, the Geocryolab’s bathymetric mapping system to the next study site (photo: V. Preskienis)

 

Rapid disappearance of perennial ice cover on Canada’s most northern Lake

March 18, 2015 in post

Canada’s most northern lake, Ward Hunt Lake, has lost its perennial ice cover in 2011 and 2012. According to scientific archives and satellite imagery, this is the first recorded occurrence of complete open water conditions on this lake, usually known for maintaining a >3.5 m thick cover even in late summer. Geocryolab member Michel Paquette shows in a newly published article in Geophysical Research Letters that the decay of the ice cover began in 2008 and is the result of a succession of warm summers from 2008 onwards. The implications of phenological changes of lake ice covers are numerous, they greatly affect limnological conditions such as thermal regime and stratification, water chemistry and lake biology.

To view the paper:
http://onlinelibrary.wiley.com/doi/10.1002/2014GL062960/abstract

 

Week #1 – Recent Cryosphere papers

January 6, 2014 in Article

Van Wychen, W., et al. (2013). “Glacier velocities and dynamic ice discharge from the Queen Elizabeth Islands, Nunavut, Canada.” Geophysical Research Letters: 2013GL058558.

Van Nieuwenhove, N. and J. P. Briner (2014). “Sea-ice, glaciers and climate dynamics of Baffin Bay and the NW Passage.” Journal of Quaternary Science 29(1): 1-1.

Bouchard, F., et al. (2013). “Vulnerability of shallow subarctic lakes to evaporate and desiccate when snowmelt runoff is low.” Geophysical Research Letters 40(23): 2013GL058635.

Strauss, J., et al. (2013). “The deep permafrost carbon pool of the Yedoma region in Siberia and Alaska.” Geophysical Research Letters 40(23): 2013GL058088. (Open Access)

Wik, M., et al. (2014). “Energy input is primary controller of methane bubbling in subarctic lakes.” Geophysical Research Letters: 2013GL058510.

An, H. and S. J. Noh “High-order averaging method of hydraulic conductivity for accurate soil moisture modeling.” Journal of Hydrology(0). (Early Access)

Kneisel, C., et al. “Application of 3D electrical resistivity imaging for mapping frozen ground conditions exemplified by three case studies.” Geomorphology(0). (Early Access)