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We investigated the response of lake algal communities to changes in glacial meltwater from the Renland Ice Cap (Greenland) through the Holocene to assess whether influxes always elicit consistent responses or novel responses. We measured sedimentary algal pigments in two proximal lakes, snow-fed Raven and glacier- and snow-fed Bunny Lake, and diatom community structure and turnover in Bunny Lake. Diatom data were not available in Raven Lake. We also modeled lake-level change in Bunny Lake to identify how glacial meltwater may have altered diatom habitat availability through time. Through a series of glacier advances and retreats over the Holocene, the algal response in Bunny Lake was relatively constant until approximately 1015 yr BP, after which there were major changes in sedimentary algal remains. Algal pigment concentrations sharply declined, and diatom species richness increased. Diatom community structure underwent three reorganizations. Until 1015 yr BP, assemblages were dominated by Pinnularia braunii and Aulacoseira pffaffiana. However, approximately 1015-480 yr BP, these species declined and Tabellaria flocculosa and Hannaea arcus became a significant component of the assemblage. Approximately 440 yr BP, A. pfaffiana increased along with species indicating elevated nitrogen. In contrast, the algal pigment records from nearby snow-fed Raven Lake showed different and minimal change through time. Our results suggest that changes in the magnitude and composition of meltwater in our two study lakes were unique over the last 1000 yr BP and elicited a non-linear threshold response absent during other periods of glacier advance and retreat. Deciphering the degree to which glaciers structure algal communities over time has strong implications for lakes as glaciers continue to recede. [ABSTRACT FROM AUTHOR]

Abstract: This paper is the first to summarize research on fluctuations of local glaciers in Greenland (e.g. ice caps and mountain glaciers independent of the Greenland Ice Sheet) during latest Pleistocene and Holocene time. In contrast to the extensive data available for fluctuations of the Greenland Ice Sheet, surprisingly little data exist to constrain local glacier extents. Much of the available research was conducted prior to wide-spread use of AMS radiocarbon dating and the advent of surface-exposure and luminescence dating. Although there is a paucity of data, generally similar patterns of local glacier fluctuations are observed in all regions of Greenland and likely reflect changes in paleoclimate, which must have influenced at least the margins of the Inland Ice. Absolute-age data for late-glacial and early Holocene advances of local glaciers are reported from only two locations: Disko (island) and the Scoresby Sund region. Subsequent to late-glacial or early Holocene time, most local glaciers were smaller than at present or may have disappeared completely during the Holocene Thermal Maximum. In general, local glacier advances that occurred during Historical time (1200–1940 AD) are the most extensive since late-glacial or early Holocene time. Historical documents and more recent aerial photographs provide useful information about local glacier fluctuations during the last ∼100 yrs. In all but one area (North Greenland), local glaciers are currently receding from Historical extents. [Copyright &y& Elsevier]

Abstract: Thirty-eight new cosmogenic (10Be) exposure ages from the Scoresby Sund region of east Greenland indicate that prominent moraine sets deposited by mountain glaciers date from 780 to 310yr, approximately during the Little Ice Age, from 11 660 to 10 630yr, at the end of the Younger Dryas cold interval or during Preboreal time, and from 13 010 to 11 630yr, during lateglacial time. Equilibrium line altitudes (ELAs) interpreted from lateglacial to Early Holocene moraines indicate summertime cooling between ∼3.9 and 6.6°C relative to today''s value, much less than the extreme Younger Dryas cooling registered by Greenland ice cores (mean-annual temperatures of ∼15°C colder than today''s value). This apparent discrepancy between paleotemperature records supports the contention that Younger Dryas cooling was primarily a wintertime phenomenon. 10Be ages of lateglacial and Holocene moraines show that mountain glaciers during the Little Ice Age were more extensive than at any other time since the Early Holocene Epoch. In addition, 10Be ages of lateglacial moraines show extensive reworking of boulders with cosmogenic nuclides inherited from prior periods of exposure, consistent with our geomorphic observations and cosmogenic-exposure dating studies in other Arctic regions. [Copyright &y& Elsevier]