Sediment dynamics in paired High Arctic lakes revealed from high‐resolution swath bathymetry and acoustic stratigraphy surveys

Abstract

High Arctic lakes are commonly used for paleoclimatic reconstructions because they are particularly sensitive to climate variability. However, the processes leading to sediment deposition and distribution in these lakes are often poorly understood. Here for the first time in the Canadian High Arctic, we present original data resulting from swath bathymetry and subbottom surveys carried out on two lakes at Cape Bounty, Melville Island. The results reveal the dynamic nature of the lakes, in which mass movement deposits and bedforms on the deltas reflect frequent slope instabilities and hyperpycnal flow activity. The analysis of the mass movement deposits reveals that small blocky debris flows/avalanches, debris flows, and a slide occurred during the Holocene. These mass movements are believed to have been triggered by earthquakes and potentially by permafrost thawing along the shoreline. Altogether, these mass movement deposits cover more than 30% of the lake floors. Additionally, the river deltas on both lakes were mapped and reveal the presence of several gullies and bedforms. The presence of gullies along the delta front indicates that hyperpycnal flows generated at the river mouth can transport sediment in different trajectories downslope, resulting in a different sediment accumulation pattern and record. The dynamic nature of these two lakes suggests that further analysis on sediment transport and distribution within Arctic lakes is required in order to improve paleoclimatic reconstructions.

Influence of North Pacific decadal variability on the western Canadian Arctic over the past 700 years

“…Counts were made by two different users and yielded very similar results in the upper part (above 167 cm), in which the first 925 varves are present (1075 CE). The error between the two counts is estimated to be less than 1.2 % (Lapointe et al, 2012), a very good number compared to other similar records (Ojala et al, 2012). Overall, the counts have been very consistent since 244 CE, implying that the varves from CBEL are well-defined and unambiguous (Lapointe et al, 2012).…”

“…The methods used to count varves rely on both visual examination of thin sections and the use of ∼ 7000 microscopic images (1024 × 768 µm) obtained using a scanning electron microscope in backscatter mode. This technique allows for the reliable identification of thin varves (< 0.4 mm), thus decreasing the chances of missing thin varves (Ojala et al, 2012). The chronology of the recent part of the record was also confirmed by radiometric dating ( 137 Cs and 210 Pb) (Cuven et al, 2011).…”

“…1-2) and the overall co-variability between the instrumental PDO and the CBEL record (Figs. 3, S2), this lag is likely due to intrinsic errors of varve chronologies (Ojala et al, 2012) rather than a mechanistic phase shift. When applying a 5-year running mean to the series, the covariability is striking (r = −0.48), especially from 1750 to 1900 (r = −0.68).…”

Supplementary material to &quot;Influence of North Pacific Decadal Variability on the Western Canadian Arctic over the past 700 years&quot;

“…Moreover, Ct-Scans of the core did not reveal any hiatus or unconformity. Finally a recent acoustic survey revealed that the coring site was devoid of mass movement deposits (Normandeau et al, 2016b). In brief, all these features are suggesting that our sedimentary record is minimally affected by erosion (Cuven et al, 2011;Lapointe et al, 2012).…”

Post-Glacial Sedimentation in Ossipee Lake, New Hampshire

“…Additional insight can be obtained through added 14 C analysis on the northern composite core. High resolution bathymetry and subbottom surveys could also provide potential insight on pathways and mechanisms of sediment transport (Normandeau et al, 2016).…”