Holocene climate changes in southern Greenland: evidence from lake sediments

Abstract

A Holocene lake sediment record is presented from Lake N14 situated on Angissoq Island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11 550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long-term trend is climate variability on a centennial time-scale that increases in amplitude after 3700 cal. yr BP. A climatic scenario related to the strength and position of the Greenland high-pressure cell and the Iceland low-pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times.

Relative sea-level change in Greenland during the last 700 yrs and ice sheet response to the Little Ice Age

“…This was followed by a relatively warm interval and a second minimum at c. 1850 A.D. (Dahl-Jensen et al, 1998;Johnsen et al, 2001). Ice core accumulation data suggest little evidence for persistent changes during the period after 1200 A.D. (Andresen et al, 2004) although Deuterium and Na ++ records all point towards a significant change in moisture source after c. 1400 A.D. that may record a strengthening of meridional circulation (Dawson et al, 2007;Hoffmann et al, 2001;Kreutz et al, 1997;Mayewski et al, 1993).…”

“…A review of palaeoclimate records from this period in Greenland shows that most identify a general shift to cooler conditions after c. 3000 cal yr B.P. associated with the onset of the neoglacial (Andresen et al, 2004;Bennike et al, 2010;Fredskild, 1983;Heggen et al, 2010;Kaplan et al, 2002). However, it is important to note that most records from c. 1400 A.D. onwards are poorly dated and of low resolution, certainly compared with their Canadian or European arctic equivalents (Kaufman et al, 2009).…”

Interaction between subsurface ocean waters and calving of the Jakobshavn Isbræ during the late Holocene

“…Atmospheric variability in the Barents Sea and Arctic Ocean modulating the outflow of sea-ice must also have played an important role for variability in the North Atlantic Ocean in the form of centennial long periods characterised by extensive 'Great Salinity Anomalies' (Andrews et al 2001a, b, c;Andrews and Giraudeau 2003;Bond et al 2001;Jennings et al 2002, Andresen et al, 2004Andresen and Björck, 2005). The influence from sea-ice transported from the Arctic Ocean may have increased during the past 1000 years modulating the East Greenland Current and affecting the North Atlantic and West Greenland region in a similar manner (in-phase relationship), likewise, melt water from a growing Inland ice-sheet may potentially have altered surrounding water masses.…”

The contribution of tephra constituents during biogenic silica determination: implications for soil and palaeoecological studies

“…Each technique has specific benefits and limitations (Ohlendurf and Storm, 2008). The alkaline extraction techniques are applied to a range of environments and archives, including soils, peat deposits, lake and marine sediments, wetland and floodplain deposits, and suspended matter in rivers (Andresen et al, 2004;Clymans et al, 2011a, b;Cornelis et al, 2010;Fernández et al, 2013;Frings et al, 2014b;Verschuren et al, 2002). In terrestrial ecosystems vegetation may buffer DSi delivery to streams and rivers (Churchman and Lowe, 2012;Struyf and Conley, 2012).…”

“…Hence, the magnitude of BSi accumulation in soils is a key component in the biological buffering capacity of the Si cycle in an ecosystem. Palaeoecologists use BSi as a proxy for diatom productivity, and apply this to infer changes in, for example, nutrient availability (Conley et al, 1993;Heathcote et al, 2014), hydrology (Andresen et al, 2004), atmospheric circulation (Harper et al, 1986;Johnson et al, 2011;Verschuren et al, 2002) and temperature (Adams and Finkelstein, 2010;Prokopenko et al, 2006).…”