Taconite Inlet Project
The Taconite Inlet Lakes Project: an Overview
R.S. Bradley, M.J. Retelle, S. D. Ludlam
D.R. Hardy, B. Zolitschka, S. F. Lamoureux, and M.S.V. Douglas.
A three year research program, focused on Lake C2 and its watershed, was initiated in 1990. The objective was to obtain an understanding of the paleoclimatic signal in varved sediments from the lake by studying the primary controls on sediment flux to the lake, and sediment transport within the lake. Table 1 lists the main factors influencing laminated sediment formation in Lake C2.
Solar radiation and other meteorological parameters were recorded at the Delta site in all three summers of the project. A second station, at 520m elevation on Echo Peak was established after the first year to obtain information on meteorological conditions in the upper section of the drainage basin, above the frequent low stratus cloud layer. Echo Peak station was located close to the median elevation of the watershed and frequently recorded temperatures higher than at the Delta site. Hydrological measurements and sediment flux samples were made on the main stream entering Lake C2, ~100m upstream of the Delta meteorological station. Further discussion of these observations is given in Hardy (1995). Meteorological data from the Lake C2 stations were compared with the longer records at Alert to provide a 40 year perspective on climatic conditions in the region. These comparisons (Hardy et al., 1996) show that sediment flux was strongly related to daily temperatures above 0° C.
Sediment traps were deployed in an array in front of the main delta of Lake C2; certain traps were recovered after significant runoff events, others were sampled on a seasonal basis. In addition, regular measurements of Secchi disk visibility were made as the season progressed, and profiles of temperature, conductivity, dissolved oxygen, transmissivity (horizontal absorption) and PAR (photosynthetically active radiation) were made at a network of sites across the lake with a Seacat SBE19 profiler (Seabird Electronics). Further details of these observations are provided in Retelle (1996) and Ludlam (1996b).
A set of short sediment cores were recovered along a transect from the inlet to the outlet of the lake, together with other cores along transects perpendicular to this transect, using both Ekman dredges and a KB corer. Detailed studies of these cores was carried out to determine if the laminations could be correlated from one location in the lake to another, and if the laminations were indeed annual. The results demonstrated the sediments are varved and that there is strong coherence between the varve thickness from widely separated cores within the lake; details of this work are given in Zolitschka (1996). Sediment flux to the lake, 'predicted' by the temperature record at Alert, closely parallels variations in mean thickness of the varves over the last 40 years (Hardy et al., 1996) enabling a long record of lamination thickness (Lamoureux and Bradley 1996) to be interpreted as a record of summer temperature variations (Bradley et al., 1996).
A set of longer sediment cores (each ~1m in length) was recovered along a transect across the lake floor, from below the oxycline to above it. We hypothesise that the preservation of varved sediments is restricted to the anoxic zone beneath the oxycline (where bioturbation is minimal), and that the presence or absence of laminations in shallow water sediments indicates changes in the depth of the oxycline over time. The results of this work, and of the paleoclimatic record in the laminated sediments from these cores, are discussed in Lamoureux and Bradley (1996).
Studies of the modern diatom ecology of the lake and streams entering the lake, were carried out throughout the project. These studies provided insight into the recent paleoenvironmental record represented by the diatom flora in the sediments and further discussion of this aspect of the study is given in Ludlam et al. (1996). The diatom record in a core which extends back to the time when Lake C2 was part of Taconite Inlet is given in Douglas et al., (1996).
Collectively, these studies provide a comprehensive evaluation of the modern environment in the Taconite Inlet area in general, and the Lake C2 watershed, in particular. By taking a systems approach, we have tried to assess the role of different factors which determine the inter-annual variations of sediment accumulation in the lake. Process-based studies are especially important in the Arctic, as there are only a few, widely separated, long-term records with which to calibrate sedimentary records. By measuring contemporary processes, a quantitative understanding of the climatic controls on sedimentation can be achieved, thereby strengthening paleoclimatic interpretations of the sedimentary record.
The results of the Taconite Inlet Project will be pubished in 1996, in a special edition of the Journal of Paleolimnology.
Acknowledgements
Research was supported by a U.S. National Science Foundation grant to the University of Massachusetts (Grant DPP-8922082). Logistical support was provided by the Canadian Department of Energy, Mines and Resources (Polar Continental Shelf Project [PCSP]). We especially thank the employees of PCSP in Resolute, and the pilots of Ken Borek Air, for assistance which was frequently above and beyond the call of duty. In addition, we thank M. Jeffries for unpublished data, and the following for field assistance during the course of this project: J. Child, P. Friedman, M. Glos, J. P. Hardy, S. O'Brien and R.J. Wolfe.
DRH also aknowledges support from the following, all of which was vital to
the success of the project: the Geological Society of America, for a
Research Grant and a Robert K. Fahnestock Memorial Research Award; Sigma Xi
for a Grant-in-Aid of Research; the Five College Canadian Studies Program;
and the University of Massachusetts Department of Geology and Geography, for
a Gloria Radke Memorial Award.
We would also like to thank those involved with field equipment support.
W.D. McCoy loaned numerous items; B. McArthur of Atmospheric Environment
Service, Canada and D. Beaubien of Yankee Environmental Systems, Inc. both
lent meteorological instruments. J. Terrell and A. Kudrikow at Univ. of
Massachusetts cheerfully responded to requests for the fabrication of
unusual items and parts. N. Pietraszkiewicz calmly and deftly handled
countless purchase orders, often on rather short notice. These efforts are
all greatly appreciated.
Lastly, as Director of the Climate Lab, Frank Keimig has been invaluable.
All of us involved have benefitted from Frank's expertise and patience with
both hardware and software, his humor, and his ability to solve multiple
problems simultaneously.
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