MULTI-PROXY LACUSTRINE RECORDS OF HOLOCENE ENVIRONMENTAL CHANGE IN ARCTIC CANADA

Lacustrine records from the Clyde region, northeastern Baffin Island, provide continuous records of Holocene environmental conditions. A 180-cm-long core from 6 m depth in lake CF3, a small (0.4 km²) lake with no significant inflow, has received the most attention. Macrofossil ¹⁴C ages from six depths provide a chronology from ~11.5 ka, the time of regional deglaciation, through to the 20th century via an overlapped surface core. Magnetic susceptibility, bulk density, loss-on-ignition (LOI), bulk total carbon (C) and nitrogen (N), bulk carbon and nitrogen stable isotopes, and chironomid and diatom taxonomic data from CF3 allow us to reconstruct the evolution of the lake since deglaciation and to compare and contrast proxy data. Taken together, the data indicate that upon deglaciation, the lake basin became productive before the landscape, both lake basin and surrounding landscape achieved maximum productivity driven by maximum summer temperature (T) between 10.2 and 8.3 ka, and since then, T and aquatic productivity decreased. The Holocene thermal maximum at Clyde led adjacent Baffin Bay, but lagged southern Baffin Island sites adjacent to the Labrador Sea. Details: Among the downcore data, LOI values have been obtained at the highest resolution (~60 yr.; n=185). Total C from 52 overlapping levels indicates that LOI faithfully represents organic carbon (r²=0.93). Bulk C and N correlate moderately well with the inverse of N-stable isotopes (r²=0.73), but poorly with C-stable isotopes (r²=0.22). Chironomid taxonomy-based July air temperature (n=11) has a high correlation with LOI and C data (r²=0.88). The core can be subdivided into five distinct zones: Zone I comprises a clean sandy unit at the base of the core; few data were collected from this zone. Zone II comprises macrofossil-rich gyttja from 10.8 to 10.2 ka. This zone has intermediate LOI/C/N values, intermediate but variable T, and contains the highest C-stable isotope and lowest C/N values of the record. Zone III, 10.2 to 8.3 ka, has the highest LOI/C/N values, highest T, relatively high C-stable isotope and relatively low N-stable isotope values. Zone IV, 10.2 to 8.3 ka, has declining LOI/C/N values, similar C-stable isotope values to Zone III, and increasing N-stable isotope values. Zone V, 8.3 ka to the top, is comprised of silty gyttja with low LOI/C/N values, low C-stable isotope and increasing N-stable isotope values.