Eastern Baffin Island Research Articles

Impacts of vertical mixing and ice-melt on N2O and CH4 concentrations in the Canadian Arctic Ocean

The sources and sinks of methane (CH4) and nitrous oxide (N2O) in the Arctic Ocean are subject to significant uncertainty, due to a combination of high spatial and temporal variability, and limited observations over relevant scales. To address this, an underway ship-board system was developed to simultaneously and continuously measure surface water CH4 and N2O concentrations in the Canadian Arctic Ocean, providing high-resolution data over a range of hydrographic regimes. Across our survey region during late summer, 2021, CH4 and N2O saturation ranged from 94% to 231% and 96%–120%, respectively. Localized CH4 and N2O maxima were observed along the cruise track, including high concentrations over the continental shelf of eastern Baffin Island, and in some waters influenced by sea ice cover or recent glacier retreat. We use our high-resolution data to examine the relationship between N2O and CH4 concentrations and a variety of oceanographic variables, demonstrating both positive correlations with salinity, which reflects the likely influence of vertical mixing, and negative correlations with salinity, indicative of ice-melt and freshwater inputs. These results build upon previous discrete CH4 and N2O observations in the Canadian Arctic, providing new information on the fine-scale distribution of these gases, and the potential underlying biogeochemical factors driving their variability. Results from our work have implications for understanding the biogeochemical cycling of Arctic Ocean CH4 and N2O under a rapidly warming climate.

Retreat and stabilization of a marine-based ice margin along a high arctic fjord-cross-shelf trough system

Multibeam bathymetric and seismostratigraphic data collected in the Clyde fjord-cross-shelf trough system (eastern Baffin Island, Canadian Arctic Archipelago) display glacial landforms and depositional assemblages that enable the identification of the maximal extent of the Laurentide Ice Sheet (LIS) margin and delineating the patterns and controls on its subsequent retreat. Additionally, 10 new sediment cores – from which seven radiocarbon ages were acquired – allow the recognition of depositional processes. Results show that, during the Last Glacial Maximum, the LIS margin extended almost to the edge of the continental shelf. Early deglaciation of the trough was marked by an initial ice-shelf collapse and rapid retreat of the ice stream, as evidenced by the absence of ice marginal landforms and the presence of extensive iceberg ploughmarks across a large portion of the outer trough. It was followed by a slow retreat and successive stabilizations of the ice margin that led to the deposition of recessional moraines and grounding-zone wedges (GZWs). Deglaciation of the fjord in the early Holocene occurred in an episodic style, whereby rapid retreat was punctuated by relatively long standstills that enabled major moraine formation. Long-term stabilizations of the ice margin in the Clyde fjord-cross-shelf trough system are interpreted to coincide with major climatic cooling events, such as the Younger Dryas and early Holocene cold reversals. Ages derived from sediment cores and previous work suggest that higher retreat rates correspond with periods of significant global sea level rise, suggesting that oceanic forcing exerted a minor control on the deglaciation. GZWs and large moraine ridges are observed at pinning points in the trough and fjord, indicating that the location of ice margin stabilizations was influenced by topography. The reconstruction of the deglaciation of the Clyde fjord-cross-shelf trough system allows us to refine deglacial models for similar systems of northeastern Baffin Island, in particular beyond the coast and along the steeper section of the fjord where chronological gaps remained.

Incorporating environmental covariates into a Bayesian stock production model for the endangered Cumberland Sound beluga population

The Cumberland Sound (CS) beluga (Delphinapterus leucas)population inhabits CS on eastern Baffin Island, Nunavut, Canada, and is listed as threatened under the Canadian Species at Risk Act. The population dynamics of CS beluga whales have been modelled in the past, but the effect of environmental covariates on these models has not previously been considered. An existing Bayesian population model fitted to CS beluga whale aerial survey data from 1990 to 2017 and harvest data from 1960 to 2017 was modified to include sea ice concentration (ICE) and sea surface temperature (SST). ICE and SST were extracted for all years from the CS study area in March and August, respectively, and incorporated into the state process component of the state-space model. The model resulted in a 2018 population estimate of 1245 (95% credible interval [CI] 564-2715) whales and an initial population estimate of 5147 (95% CI 1667-8779). Determining sustainable harvest by calculating the probability of population decline estimated 30% probability of decline after 10 yr with a harvest of ~15 whales annually. Compared to the previous model without environmental covariates, which followed a relatively linear trajectory, our model had more noticeable peaks and troughs in the population trend and wider CIs. The model suggested harvest levels be reduced by ~7 individuals for a management goal with a low risk of decline. The novelty of this approach for beluga whales provides an opportunity for further model development via the addition of various other abiotic and biotic variables related to beluga whale ecology.

Polar bear diet composition reveals spatiotemporal distribution of Arctic marine mammals across Nunavut, Canada

Climate warming and associated physical and biological changes will likely force widespread species redistribution, particularly in polar environments. However, tracking such distributional shifts is difficult. The dietary habits of apex predators, like polar bears (Ursus maritimus), may provide early signals of distributional change in prey populations. We used harvest-based sampling to investigate the spatial feeding patterns of polar bears across Nunavut from 2010 to 2018 (n = 1570) and identify spatiotemporal clusters of different prey based on predator diet estimates. Quantitative fatty acid signature analysis and the Getis-Ord Gi* statistic identified spatial clusters of high or low dietary proportions (i.e., “hot spots” and “cold spots”) reflecting seasonal and spatial availability of prey. Ringed seal (Pusa hispida) was the primary prey of bears throughout Nunavut followed by bearded seal (Erignathus barbatus), although proportional consumption varied spatially. A consistent ringed seal consumption hot spot was found in Gulf of Boothia indicating the importance of year-round availability of ringed seals. Spatial clusters of bearded seal and Atlantic walrus (Odobenus rosmarus rosmarus) throughout Foxe Basin suggested overlapping seasonal distributions and high regional abundance. Bears had consistently high dietary levels of harbour seal (Phoca vitulina) around Southampton Island and along the western coast of Hudson Bay suggesting a possible year-round concentration of this prey. Hot spots of harp seal (Pagophilus groenlandicus) consumption were evident throughout Davis Strait and a spring-summer hot spot around Jones Sound was consistent with harp seal migratory patterns. Year-round beluga whale (Delphinapterus leucas) hot spots were found along eastern Baffin Island and southern Viscount Melville Sound providing new knowledge of local conditions that promote polar bear predation or scavenging. Narwhal (Monodon monoceros) were less susceptible to predation with only one spatial cluster of high consumption appearing during spring-summer in Barrow Strait. Bowhead whale (Balaena mysticetus) hot spots occurred around south-western Foxe Basin and seasonally in southern Viscount Melville Sound suggesting carcasses are locally accessible to bears and may act as a supplemental food source in particular areas and seasons. The congruence of polar bear feeding habits and known prey distribution suggests polar bears serve as ecological indicators and ongoing monitoring of their diets may reveal regional and broad-scale changes in prey population distributions and Arctic ecosystem functioning.

Postglacial sea-level lowstand on Cumberland Peninsula, Baffin Island, Nunavut

This study investigates the postglacial sea-level history of eastern Cumberland Peninsula, a region of Baffin Island, Nunavut, where submerged terraces were documented in the 1970s. The elevation gradient of emerged postglacial marine-limit deltas and fiord-head moraines led Arthur Dyke to propose a conceptual model for continuous postglacial submergence of the eastern peninsula. Multibeam mapping over the past decade has revealed eight unequivocal submerged deltas at 19–45 m below present sea level (b.s.l.) and other relict shore-zone landforms (boulder barricade, spits, and sill platform) at 16–51 m b.s.l. Over a distance of 115 km from Qikiqtarjuaq to Cape Dyer, the submerged coastal features increase in depth toward the east, with a slope (0.36 m/km) less than that of the marine-limit shoreline previously documented (0.58–0.62 m/km). The submerged ice-proximal deltas, deglacial ice limits, and radiocarbon ages constrain the postglacial lowstand between 9.9 and 1.4 ka cal BP. The glacial-isostatic model ICE-7G_NA (VM7) computes a lowstand relative sea level at 8.0 ka, the depth of which increases eastward at 0.28 m/km. The difference between observed and model-derived lowstand depths ranges from 1 m in the west to 10 m in the east and the predicted tilt is significantly less than observed (p = 0.0008). The model results, emerging data on Holocene glacial readvances on eastern Baffin Island, and evidence for proglacial delta formation point to a Cockburn (9.5–8.2 ka) age for the lowstand, most likely later in this range. This study confirms the 1970s conceptual model of postglacial submergence in outer Cumberland Peninsula and provides field evidence for further refinement of glacial-isostatic adjustment models.

Mapping Arctic cetaceans from space: A case study for beluga and narwhal.

Emergence of new technologies in remote sensing give scientists a new way to detect and monitor wildlife populations. In this study we assess the ability to detect and classify two emblematic Arctic cetaceans, the narwhal (Monodon monoceros) and beluga whale (Delphinapterus leucas), using very high-resolution (VHR) satellite imagery. We analyzed 12 VHR images acquired in August 2017 and 2019, collected by the WorldView-3 satellite, which has a maximum resolution of 0.31 m per pixel. The images covered Clearwater Fiord (138.8 km2), an area on eastern Baffin Island, Canada where belugas spend a large part of the summer, and Tremblay Sound (127.0 km2), a narrow water body located on the north shore of Baffin Island that is used by narwhals during the open water season. A total of 292 beluga whales and 109 narwhals were detected in the images. This study contributes to our understanding of Arctic cetacean distribution and highlights the capabilities of using satellite imagery to detect marine mammals.

Settler colonialism’s container technologies: photographing crates in the Canadian Arctic (1926–1953)

ABSTRACT Wooden crates are a recurring subject in the visual archive of settler colonialism in Canada’s Arctic, appearing on the shores of eastern Baffin Island throughout the first half of the twentieth century. Reading some of the hundreds of photographs that appear in the holdings of Library and Archives Canada in Ottawa, this essay charts the symbolic and political work that crates performed in the settler colonial imaginary. It draws on David L. Eng’s call to examine the ‘colonial object relations’ that have split Indigenous subjects into ‘good and bad objects’ in the liberal imaginary to propose that wooden crates are symptomatic of settler colonialism’s unconscious drive to make and unmake Inuit subjects into citizens in response to the demands of national and transnational political events. Tracing the intersection of crates, photography and ballot boxes in the archive, the essay examines the settler colonial state’s attempts at imposing and consolidating power, but also points to the practices of continuity and resistance enacted by Inuit subjects.

Mercury in Ringed Seals (Pusa hispida) from the Canadian Arctic in Relation to Time and Climate Parameters.

Mercury is found in Arctic marine mammals that are important in the diet of northern Indigenous peoples. The objectives of the present long‐term study, spanning a 45‐yr period, were to 1) investigate the temporal trends of total mercury (THg; muscle and liver) and selenium (Se; liver) in ringed seals (Pusa hispida) from different regions of the Canadian Arctic; and 2) examine possible relationships with age, diet, and climate parameters such as air temperature, precipitation, climatic indices, and ice‐coverage. Ringed seals were collected by hunters in northern communities in the Beaufort Sea, Central Arctic, Eastern Baffin Island, Hudson Bay, and Ungava/Nunatsiavut regions (Canada) between 1972 and 2017. Mercury levels did not change through time in seal liver, but THg levels in muscle decreased in seals from Hudson Bay (−0.91%/yr) and Ungava/Nunatsiavut (−1.30%/yr). Carbon stable isotope values in seal muscle decreased significantly through time in 4 regions. Selenium‐to‐THg ratios were found to be >1 for all years and regions. Variation partitioning analyses across regions indicated that THg trends in seals were mostly explained by age (7.3–21.7%), climate parameters (3.5–12.5%), and diet (up to 9%); climate indices (i.e., Arctic and North Atlantic Oscillations, Pacific/North American pattern) explained the majority of the climate portion. The THg levels had a positive relationship with Arctic Oscillation for multiple regions. Associations of THg with air temperature, total precipitation, and sea‐ice coverage, as well as with North Atlantic Oscillation and Pacific/North American pattern were found to vary with tissue type and geographical area. Environ Toxicol Chem 2020;39:2462–2474. © 2020 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. Reproduced with the permission of the Minister of Fisheries and Oceans Canada.

Long-term Declines in the Size of Northern Fulmar (<i>Fulmarus glacialis</i>) Colonies on Eastern Baffin Island, Canada

We censused three colonies of Northern Fulmars (Fulmarus glacialis) along eastern Baffin Island, Canada, that were estimated to support 155 000 breeding pairs in 1973, but had not been adequately counted since then. The colonies were surveyed in July and August 2018 using photographs taken from a helicopter or a drone. The combined estimated colony sizes were 36 500 pairs, much smaller than historical estimates. Although the 1973 estimates were coarse, this difference represents an apparent 3+% annual decline in numbers at each colony over approximately four decades or more than 87% over three generations (66 years). Several factors may be contributing to these declines, including changes in winter food supplies and the susceptibility of fulmars to fisheries bycatch. We recommend efforts to survey the remaining major fulmar colonies in Arctic Canada to assess the overall population size and trends, and allow for further analyses of potential population drivers.

First Report of Scoters (<i>Melanitta</i> spp.) along Eastern Baffin Island, Nunavut, Canada

In September of 2017 and 2018, we observed hundreds of scoters (Melanitta spp.) in fiords in Arctic Canada, approximately 1100 – 1800 km north of their previous northernmost observations. Given the remote locations and timing of observations, we do not know if these represent previously undiscovered areas where birds moult or new movements to Arctic locations. Moreover, the provenance of these sea ducks is unclear, as no evidence of movements to this region was indicated by large-scale satellite tracking of North American scoters during the last decade.

Retreat Pattern of Glaciers Controls the Occurrence of Turbidity Currents on High‐Latitude Fjord Deltas (Eastern Baffin Island)

AbstractGlacier and ice sheet mass loss as a result of climate change is driving important coastal changes in Arctic fjords. Yet limited information exists for Arctic coasts regarding the influence of glacial erosion and ice mass loss on the occurrence and character of turbidity currents in fjords, which themselves affect delta dynamics. Here we show how glacial erosion and the production of meltwaters and sediments associated with the melting of retreating glaciers control the generation of turbidity currents in fjords of eastern Baffin Island (Canada). The subaqueous parts of 31 river mouths along eastern Baffin Island were mapped by high‐resolution swath bathymetry in order to assess the presence or absence of sediment waves formed by turbidity currents on delta fronts. By extracting glaciological and hydrological watershed characteristics of these river mouths, we demonstrate that the presence and areal extent of glaciers are a key control for generating turbidity currents in fjords. However, lakes formed upstream during glacial retreat significantly alter the course of sediment routing to the deltas by forming temporary sinks, leading to the cessation of turbidity currents in the fjords. Due to the different deglaciation stages of watersheds in eastern Baffin Island, we put these results into a temporal framework of watershed deglaciation to demonstrate how the retreat pattern of glaciers, through the formation and filling of proglacial lakes, affects the turbidity current activity of deltas.

Algal pigments in Arctic lake sediments record biogeochemical changes due to Holocene climate variability and anthropogenic global change

In order to better constrain the limnological impacts from recent climate change relative to those of the Holocene, we developed a high-resolution multi-proxy paleoenvironmental record from a small lake on eastern Baffin Island, Arctic Canada. Carbon and nitrogen elemental and isotopic compositions from sediment organic matter, algal pigments, and diatom assemblages are integrated to provide robust indices of paleoclimatic variability. In particular, the ratio between individual carotenoid pigments (lutein:diatoxanthin) reveals a shift in dominant primary production from ‘green’ taxa (chlorophytes, higher plants, and bryophytes) during the Holocene Thermal Maximum (HTM) to ‘brown’ taxa (diatoms and chrysophytes) over the mid- to late Holocene. Green pigment abundance appears most sensitive to mean summer temperatures, and their increased relative abundance in the past serves as an indicator of warm times. Regionally, the HTM occurred shortly after local deglaciation (10 ka), persisting until ~7 ka. This timing agrees with that revealed by chironomid assemblages and ice-core records elsewhere in the Canadian Arctic, but is significantly earlier than suggestions from palynology on Baffin Island. This study provides additional evidence that this discrepancy represents the ecesis for higher plant dispersal and colonization on distal, freshly deglaciated landscapes. Pigment and diatom data indicate that mid Holocene cooling began between 7 and 6 ka, intensifying after 3 ka. All proxies show pronounced change after 1.5 ka, with the greatest divergence from average Holocene values occurring during the Little Ice Age (LIA), supporting the growing consensus that the LIA was the coldest multi-centennial interval of the Holocene. In the twentieth century, most proxies, including sedimentary carotenoid ratios, abruptly returned to a similar state as the Holocene Thermal Maximum, while diatom species assemblages present a more muted response. This underscores that anthropogenic alteration of the Earth system has created conditions with no exact analog in the past 10,000 years. Collectively, these results add new information on the dimensions of Arctic lake responses to Holocene climate change, which in turn can be used to reconcile paleoclimate reconstructions from diverse proxies.

Estimates of Minimum Population Size for Walrus near Southeast Baffin Island, Nunavut

To support management objectives in Canada and Greenland, joint research between the Department of Fisheries and Oceans and Greenland Institute of Natural Resources was begun in 2005. Direct counts were used to determine the Minimum Counted Population (MCP) in summer around SE Baffin Island. Aerial surveys examined the coast from roughly the Saddleback Island in northern Hudson Strait to Isabella Bay on eastern Baffin Island but concentrated on the area between Loks Land and Cape Dyer. The maximum count was obtained on 3–4 September 2007 during boat surveys. The MCP ranged from 716 (in 2006) to 1,056 (2007). Using the largest MCP adjusted with published maximum estimates of the proportion of walrus hauled out concurrently, we estimated 1,420 (95% CI: 1,219–1,622) walrus were present. In addition, four walrus had been fitted with satellite relayed data logger tags prior to the maximum counts in 2007. Using the simple proportion of ‘tags dry’ on 3 September to adjust counts on 3 and 4 September 2007 provided an estimate of 2,102 (CI = MCP-4,482). Using the proportion of time dry immediately preceding the survey to adjust the maximum count produced an estimate of 2,502 (CI = 1,660–3,345) walrus were present in Hoare Bay. We conclude approximately 2,100–2,500 walrus were present in Hoare Bay in late summer 2007. This number is a negatively biased estimator of the population of walrus around SE Baffin Island and in the Hudson Bay–Davis Strait stock as a whole. Broader survey coverage in a short period and more detailed information on the movement of walrus between Greenland and Canada and the summer dispersal of these animals within Canada are required to improve population estimates.

Mercury speciation in brain tissue of polar bears (Ursus maritimus) from the Canadian Arctic

Methylmercury (MeHg) is a neurotoxicant that has been found at elevated concentrations in the Arctic ecosystem. Little is known about its internal dose in wildlife such as polar bears. We measured concentrations of mercury (Hg) in three different brain regions (cerebellum, frontal lobe and brain stem) of 24 polar bears collected from the Nunavik, Canada between 2000 and 2003. Speciation of Hg was measured by High Performance Liquid Chromatography coupled to Inductively Coupled Plasma Mass Spectroscopy (HPLC–ICP-MS). Concentrations of mean total Hg in brain tissue were up to 625 times lower (0.28±0.07mgkg−1 dry weight (dw) in frontal lobe, 0.23±0.07mgkg−1 dw in cerebellum and 0.12±0.03mgkg−1 dw in brain stem) than the mean total Hg concentration previously reported in polar bear liver collected from Eastern Baffin Island. Methylmercury (MeHg) accounted for 100% of the Hg found in all three brain regions analyzed. These results suggest that polar bear might reduce the toxic effects of Hg by limiting the uptake into the brain and/or decrease the rate of demethylation so that Hg can be excreted from the brain more easily. The toxicokinetics and the blood–brain-barrier mechanisms of polar bears are still unknown and further research is required.

A 2000-yr-long multi-proxy lacustrine record from eastern Baffin Island, Arctic Canada reveals first millennium AD cold period

We generate a multi-proxy sub-centennial-scale reconstruction of environmental change during the past two millennia from Itilliq Lake, Baffin Island, Arctic Canada. Our reconstruction arises from a finely subsectioned 210Pb- and 14C-dated surface sediment core and includes measures of organic matter (e.g., chlorophyll a; carbon–nitrogen ratio) and insect (Diptera: Chironomidae) assemblages. Within the past millennium, the least productive, and by inference coldest, conditions occurred ca. AD 1700–1850, late in the Little Ice Age. The 2000-yr sediment record also reveals an episode of reduced organic matter deposition during the 6th–7th century AD; combined with the few other records comparable in resolution that span this time interval from Baffin Island, we suggest that this cold episode was experienced regionally. A comparable cold climatic episode occurred in Alaska and western Canada at this time, suggesting that the first millennium AD cold climate anomaly may have occurred throughout the Arctic. Dramatic increases in aquatic biological productivity at multiple trophic levels are indicated by increased chlorophyll a concentrations since AD 1800 and chironomid concentrations since AD 1900, both of which have risen to levels unprecedented over the past 2000 yr.

Killer whale (Orcinus orca) photo-identification in the eastern Canadian Arctic

We identified individual killer whales (Orcinus orca) using recent (2004-09) photographs to obtain a minimum count of whales that use eastern Canadian Arctic waters. Fifty-three individuals were identified from nine different sightings; 11 individuals from western Hudson Bay sightings and 42 from the areas around northern and eastern Baffin Island. One whale was resighted: an adult female or large juvenile photographed 17 days and 375 km apart at Churchill, Manitoba, and off-shore of Rankin Inlet, Nunavut, in August 2007. With only one individual re-sighted, the number of individuals that use this area is likely much larger. No re-sightings occurred between Arctic killer whales and individuals photographed off the coast of Newfoundland. Our results represent the minimum number of killer whales sighted in eastern Canadian Arctic waters and provide the foundation for further killer whale research. Little is known about Arctic killer whales and, as a top predator, it is unclear what effect they have on Arctic marine ecosystems.Keywords: Abundance; Baffin Island; Canada; distribution; High Arctic; Hudson Bay; photographs(Published: 23 May 2011)Citation: Polar Research 2011, 30, 7203, DOI: 10.3402/polar.v30i0.7203

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20° latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the 206Pb/ 207Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17–26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb–Pb co-isotopic plot ( 206Pb/ 207Pb vs. 208Pb/ 206Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.

Relationship between Holocene climate variations over southern Greenland and eastern Baffin Island and synoptic circulation pattern

Abstract. Lake pollen records from southwest Greenland and eastern Baffin Island show strong regionalism in climate trends of the last 7000 cal years. July surface air temperature reconstructions from pollen indicate larger amplitude cooling in southwest Greenland (>3.0°C) than in eastern Baffin Island (<1.0°C). This west-east gradient in climate change is consistent with August sea-surface temperature reconstructions from dinocyst records that indicate decreasing temperature and/or strength of the North Atlantic Current to the east during the Holocene while the eastern Canadian margins under the Labrador Current influence display slight warming. Complementary to air and sea-surface temperature records, the lake pollen data led to reconstruct increased cloudiness in southern Greenland, which points to increasing cyclonic activity since 7000 cal years BP west of Greenland. Together, the terrestrial and marine records of the northwest North Atlantic therefore suggest a shift from a dominant NAO+ during the early-mid Holocene to dominant NAO- in the late Holocene.

Holocene and Last Interglacial cloudiness in eastern Baffin Island, Arctic CanadaThis article is one of a series of papers published in this Special Issue on the themePolar Climate Stability Network.GEOTOP Publication 2008-0027.

This study presents Last Interglacial and Holocene vegetation and climate changes at Fog Lake (67°11′N, 63°15′W) on eastern Baffin Island, Arctic Canada. The vegetation cover is reported as vegetation structural types (or biomes). July air temperature and sunshine during the growing season (June–July–August–September) were reconstructed from pollen assemblages using the modern analogue technique. The vegetation of the Last Interglacial period evolved from a prostrate dwarf-shrub tundra to a low- and high-shrub tundra vegetation. The succession of four Arctic biomes was distinguished from the Last Interglacial sediments, whereas only one Arctic biome was recorded in the Holocene sediments. From ca. 8300 cal. years BP to present, hemiprostrate dwarf-shrub tundra occupied the soils around Fog Lake. During the Last Interglacial, growing season sunshine was higher than during the Holocene and July air temperature was 4 to 5 °C warmer than present. A principal component analysis helped in assessing relationship between floristic gradients and climate. The major vegetation changes through the Last Interglacial and Holocene were driven by July air temperature variations, whereas the minor, or subtle, vegetation changes seem rather correlated to September sunshine. This study demonstrates that growing season sunshine conditions can be reconstructed from Arctic pollen assemblages, thus providing information on feedbacks associated with cloud cover and summer temperatures, and therefore growing season length.

Methodological basis for quantitative reconstruction of air temperature and sunshine from pollen assemblages in Arctic Canada and Greenland

This study presents a modern database including 831 pollen assemblages from lakes of the Boreal, Subarctic and Arctic biomes of North America and Greenland, and corresponding temperature, sunshine and precipitation. Pollen data include the 39 most common vascular taxa (18 woody plants and 21 herbs). Multivariate ordinations using correspondence analysis (CA) and canonical correspondence analysis (CCA) reveal that temperature and sunshine account, respectively, for 45.5% and 44.4% of the variance within pollen assemblages, whereas precipitation only accounts for 10.2% of total variance. CCA further demonstrates that the climatic information encapsulated in pollen assemblages is not the same for the three biomes. In the Boreal biome, precipitation and temperature account for most of the variance, whereas sunshine and precipitation are more determinant in the Subarctic biome, and the temperature and sunshine seem to exert the main control on the pollen distribution in the Arctic biome. The modern analogue technique (MAT) and CCA regressions were tested for reconstructing climate parameters. MAT yields better results than CCA regressions and validation tests indicate a root mean square error (RMSE) of 1.35 °C for July air temperature, 2.3% for July sunshine, 3.10 °C for January air temperature and 143 mm for annual precipitation. Two examples of reconstructions are presented from recent (<450 years) lake-sediment cores of eastern Baffin Island, Arctic Canada and southwest Greenland. They demonstrate that July air temperature and July sunshine can be reconstructed independently from Arctic pollen assemblages, but January air temperature and annual precipitation must be interpreted with caution. They also suggest that reconstruction of past sunshine variations can serve to document climate changes at synoptic scale including the North Atlantic Oscillation (NAO).