Vegetation and climate of the last interglacial on Baffin Island, Arctic Canada

Sediment cores recovered from three mid-arctic lakes on Cumberland Peninsula, eastern Baffin Island, Arctic Canada, contained two units of unconformably superimposed organic sediment (gyttja), the upper of which represented sedimentation during the Holocene. Radiocarbon ages on aquatic macrofossils from the lower gyttja suggested it to be > 50 ka BP, while luminescence ages from two cores constrained the age of this sediment to > 90 and < 130 ka BP, that is, encompassing the last interglacial. Pollen spectra from these cores were used to reconstruct past vegetation and climate of the Holocene and last interglacial. In each core, last interglacial sediments yielded remarkably high pollen concentrations, and included far greater percentages of shrub (Betula and Alnus) pollen grains than did overlying Holocene sediments. Numerical comparisons of fossil pollen assemblages to a data set of 400 modern high-latitude lake sediment samples revealed that the last interglacial vegetation of east-central Baffin Island was Low Arctic in character, comparable to present-day southwest Greenland. From applications of both correspondence analysis regression and best modern analogue methodologies, we infer July air temperatures of the last interglacial to have been 4 to 5 °C warmer than present on eastern Baffin Island, which was warmer than any interval within the Holocene. On these grounds, we ascribe the lower lacustrine unit in these lakes to the climatic optimum of the last interglacial, ca. 117 to 130 ka BP (Marine Isotopic Stage 5e).