We welcome the opportunity to respond to Gajewski 's [2008] comments on our study [ Antoniades et al. , 2007, hereinafter referred to as A07]. We demonstrate here that his assertions are not supported by the evidence and that the conclusions in A07 are based on a sound interpretation of the data.
Paleohydrological connections and pathways within Nettilling Lake, the largest lake in the Canadian Arctic Archipelago (Baffin Island, Canada), remain poorly known. This knowledge gap hinders our ability to reliably infer past environmental changes that could provide clues to the future evolution of this region with rapid environmental change at high latitudes. The lake is currently fed by freshwaters from its catchment and drains westward into the Foxe Basin via the Koukdjuaq River. However, its early hydrological connections following the last deglaciation are thought to have been complex, when marine waters from the postglacial Tyrell Sea initially invaded the Nettilling basin from the west, followed by a brief reversal when Atlantic waters fed the basin from the east via the Cumberland Sound and Nettilling Fjord. To test this hypothesis, we investigated the lithology, sedimentology and geochemistry of various sediment archives from the easternmost sector of the lake. The multi-proxy data revealed three successive phases: an initial glaciomarine phase (8300 - 7300 cal. BP), a brackish phase (7300 - 6000 cal. BP) and a lacustrine freshwater phase (6000 - present). Our results support the hypothesis formulated by Blake (1966) of temporary hydrological connectivity between the Foxe Basin in the west, followed by a link with the Atlantic Ocean in the east via the Cumberland Sound before marine waters retreated due to differential glacio-isostatic uplift that forced the basin to be progressively occupied by the fresh waters of the present-day Nettilling Lake.
Concerns about the effects of global warming on Arctic environments have stimulated multidisciplinary research into the history of their long-term climatic and environmental variability to improve future predictions of climate in these remote areas. Here we present the first palaeolimnological study for Southampton Island using analyses of chironomids supported by sedimentological analyses, carried out on a 1 m long core retrieved from a lake located in the northeastern part of the island. This core was made up of marine sediments underneath 65 cm of freshwater lake sediments. A marine shell, humic-acids and chironomid head capsules were used to date this sequence. The Holocene environmental history of the lake consisted of two major contrasting periods. The first one, between about 5570 and 4360 cal. yr BP, was climatically unstable, with common postglacial chironomid taxa such as Corynocera oliveri-type, Paracladius and Microspectra radialis-type. This period also corresponded to the highest chironomid-inferred August air temperature (10°C) for the whole record and to significant increases in major chemical elements as detected by x-ray fluorescence. During the second period, which lasted from about 3570 cal. yr BP until the present, limnological conditions seemed to stabilize after a change to cold oligotrophic chironomid taxa, such as Heterotrissocladius subpilosus-group, with no major variations in the abundance of chemical elements. Inferred August air temperatures ranged between 8 and 9°C. This study provided unique information on the timing of the Holocene Thermal Maximum in the Foxe Basin area, a region with very little information available on long-term climate change. This region showed, so far, relatively few signs of recent climatic change, as opposed to other regions in the High Arctic.
The need for better understanding of long-term climate and environmental variability in the Foxe Basin (Nunavut, Canada) is highlighted by the major environmental changes in this highly sensitive region, which occupies a transitional position between areas undergoing drastic and more subtle changes in the High and Low Canadian Arctic over the course of the last millennium, respectively. However, high-resolution long-term climate records remain scarce in the Foxe Basin region even though it is of key importance to understanding Holocene climate evolution since the last deglaciation. In order to reconstruct the regional postglacial climatic and environmental variability, we adopted a multi-proxy paleolimnological approach analysing sedimentary records retrieved from Nettilling Lake on southern Baffin Island, involving elemental geochemistry from high-resolution µ-XRF analyses, diatom assemblage composition and oxygen isotope records from fossil diatom silica (δ18Odiatom). The oxygen isotope composition of diatoms (δ18Odiatom) yields extremely large δ18Odiatom variations in the core of more than 13‰ which are mainly driven by changes in the isotopic composition of the lake water due to a shift from glacio-marine to brackish (at ca. 7400 yr cal BP) towards lacustrine conditions (at ca. 6000 yr cal BP) associated with decreasing salinity also documented by shifts in the composition of diatom assemblages. Our study provides evidence that paleo-salinity can be inferred from δ18Odiatom. Additionally, in the lacustrine section of the core,, δ18Odiatom may also serve as a proxy for past air temperatures recording a late Holocene cooling of about 4°C for the greater Baffin region. Furthermore, the results obtained from our study provide new insights into the timing of regional glacier retreat (ca. 8300 cal BP) and the duration of the postglacial marine invasion (from ca. 7400 cal BP to ca. 6000 cal. BP), thereby complementing ongoing research of postglacial environmental dynamics in the Foxe Basin and on south-western Baffin Island.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)