Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Clim. Past Discuss., 11, 5401–5438, 2015 www.clim-past-discuss.net/11/5401/2015/ doi:10.5194/cpd-11-5401-2015 CPD © Author(s) 2015. CC Attribution 3.0 License. 11, 5401–5438, 2015 This discussion paper is/has been under review for the journal Climate of the Past (CP). Impact of Holocene Please refer to the corresponding final paper in CP if available. climate variability Impact of Holocene climate variability on T. Guillemot et al. lacustrine records and human Title Page settlements in South Greenland Abstract Introduction T. Guillemot1, V. Bichet1, A. Simonneau2, D. Rius1, C. Massa1, E. Gauthier1, Conclusions References 1 1 H. Richard , and M. Magny Tables Figures 1Université de Bourgogne/Franche-Comté, Laboratoire Chrono-environnement, CNRS UMR 6249, 16 route de Gray 25030 Besançon, France J I 2 Université d’Orléans, ISTO, CNRS UMR 7327, 1A rue de la Férollerie 45071 Orléans, France J I Received: 16 October 2015 – Accepted: 4 November 2015 – Published: 17 November 2015 Back Close Correspondence to: T. Guillemot ([email protected]) Full Screen / Esc Published by Copernicus Publications on behalf of the European Geosciences Union. Printer-friendly Version Interactive Discussion 5401 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Abstract CPD Due to its sensitivity to climate changes, south Greenland is a particularly suitable area to study past global climate changes and their influence on locale Human settlements. 11, 5401–5438, 2015 A paleohydrological investigation was therefore carried out on two river-fed lakes: Lake 5 Qallimiut and Little Kangerluluup, both located close to the Labrador Sea in the historic Impact of Holocene farming center of Greenland. Two sediment cores (QAL-2011 and LKG-2011), span- climate variability ning the last four millennia, were retrieved and showed similar thin laminae, described by high magnetic susceptibility and density, high titanium and TOC / TN atomic ratio, T. Guillemot et al. and coarse grain size. They are also characterized either by inverse grading followed by 10 normal grading or by normal grading only and a prevalence of red amorphous particles and lignocellulosic fragments, typical of flood deposits. Title Page Flood events showed similar trend in both records: they mainly occurred during Abstract Introduction cooler and wetter periods characterized by weaker Greenlandic paleo-temperatures, substantial glacier advances, and a high precipitation on the Greenlandic Ice Sheet and Conclusions References 15 North Atlantic ice-rafting events. They can therefore be interpreted as a result of ice and Tables Figures snow-melting episodes. They occurred especially during rapid climate changes (RCC) such as the Middle to Late Holocene transition around 2250 BC, the Sub-boreal/Sub- J I atlantic transition around 700 BC and the Little Ice Age (LIA) between AD 1300 and AD 1900, separated by cycles of 1500 years and driven by solar forcing. These global J I 20 RCC revealed by QAL-2011 and LKG-2011 flood events may have influenced Human Back Close settlements in south Greenland, especially the paleo-Eskimo cultures and the Norse settlement, and have been mainly responsible for their demise. Full Screen / Esc Printer-friendly Version 1 Introduction Interactive Discussion The Holocene appears to be a steady climatic period in comparison with older glacial 25 episodes, as climate evolution was not linear but showed several oscillations (O’Brien et al., 1995; Mayewski et al., 2004; D’Andrea et al., 2011; Larsen et al., 2012), result- 5402 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ing from various forcing mechanisms such as solar activity (Bond et al., 2001; Magny, 2013) volcano emissions (Miller et al., 2012; Sigl et al., 2013) and/or ocean/atmosphere CPD interactions (Hurrell and Denser, 2010; Knudsen et al., 2011). It is of prime importance 11, 5401–5438, 2015 to establish their spatial influence and phasing in order to understand natural climate 5 oscillations and their influence on past Human societies and thus to create better pre- dictive climatic models. Indeed, even if current global warming is mainly the result of Impact of Holocene an anthropogenic pressure, the contribution of natural climate variability cannot be ex- climate variability cluded and may explain the recent rapid rise in temperatures (Chylek et al., 2004; Solanki et al., 2004). T. Guillemot et al. 10 Projected climate scenarios predict a rise in surface temperature associated to an increase in the frequency and intensity of flood events in the coming decades (IPCC, Title Page 2013), especially in the Arctic region, which is very sensitive to climate changes (Ser- reze and Barry, 2011). Due to its proximity to the Greenlandic Ice Sheet (GIS), the polar Abstract Introduction front and the adjacent North Atlantic oceanic currents, south Greenland is a particularly Conclusions References 15 suitable area to record in natural archives past global climate changes and their asso- ciated forcing mechanisms at high resolution (Fig. 1a). While numerous proxy records Tables Figures have been used to infer past temperature in the Arctic (D’Andrea et al., 2011; McKay and Kaufman, 2014; Millet et al., 2014), few records have been used to infer past J I hydrological activity (Sundqvist et al., 2014) despite the extreme importance of hydro- J I 20 logical conditions for Arctic ecosystems and their potential feedback on global climate (MacDonald et al., 2000). Back Close To assess of past hydrological conditions during the Holocene, a sedimentological Full Screen / Esc multiproxy approach was performed, compiling physical (magnetic susceptibility, den- sity and grain size) and geochemical (X-ray fluorescence, X-ray di◆raction, elemental Printer-friendly Version 25 analyses and organic geochemistry) measurements, on two lacustrine cores. They were retrieved from two river-fed lakes: Lake Qallimiut and Little Kangerluluup located Interactive Discussion between the GIS and the Labrador Sea in the Vatnahverfi, known as the archeological farming center of Greenland where two agropastoral phases settled (the Norse period between AD 986 and ca. AD 1450 and over the last century, since the 1920s). Thus, 5403 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | this study reconstructs at high resolution the global climatic variations and the large scale drivers of Greenlandic climate though hydrological changes in lacustrine catch- CPD ments that may have influenced past Human settlements (i.e. vulnerability, adaptation 11, 5401–5438, 2015 strategies, demise, etc. ) during the last four millennia. Impact of Holocene 5 2 Settings climate variability 2.1 Localization and climate T. Guillemot et al. The study area is located between the GIS and the Labrador Sea (Fig. 1a and b). Due to this geographical position, the local climate is mainly influenced by oceanic currents, Title Page such as cold polar waters (< 0 ◦C) of the eastern Greenland current and warm waters 10 (+ 4 ◦C) of the Irminger current, which mix to the west of Kap Farvel (Bond et al., Abstract Introduction 1997). The area is also windy with strong and relatively warm foehn winds blowing Conclusions References from the ice cap throughout the year, that are responsible for dryness. Meteorological data of the last 60 years are characteristic of a sub-oceanic climate, with a mean annual Tables Figures temperature of 0.9 ◦C, a yearly precipitation of 907 mm, 211 days with frost and 61 days 15 of snow per year (Cappelen et al., 2001; Cappelen, 2014). J I 2.2 The Qallimiut lake system J I Back Close Lake Qallimiut (60◦4302700 N; 45◦2301200 E; 40 ma.s.l.) is a proglacial lake located close to the hamlet of Qallimiut ca. 2 km to the south, near the Alluitsup Kangerlua fjord Full Screen / Esc (Fig. 1c). It is aligned through a north-west/south-east axis with a surface of ca. 82 ha Printer-friendly Version 20 and a maximum depth of 26 m. Two main tributaries feed it (on the north-west and the east shores respectively) while a single outlet drains it directly in the Alluitsup Kanger- Interactive Discussion lua fjord (Fig. 1c). Its catchment, composed of granites (geological survey of Denmark and Greenland; http://www.geus.dk), has a surface of 112 km2 and a catchment to lake ratio around 137. It includes around twenty upstream lakes, making Lake Qallimiut the 25 last sediment trap of this catchment (Fig. 1c). Less than ten ruins, dated from the Norse 5404 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | period, were inventoried in the catchment with only two sites directly found around the lake (Madsen et al., 2009). These two Norse archaeological sites have already been CPD surveyed. Ruins group E77, a medium-sized farmstead, is located in the north-west 11, 5401–5438, 2015 part of the lake and was formerly excavated in AD 1880 (Holm, 1883; Madsen, 2014), 5 and ruins group E77a, near the coast, seems to be a large, highly eroded farmstead (Madsen, 2014). Nowadays, two recent farms can be found on the north and south Impact of Holocene shores of the lake (the largest one is located near the lake outlet). climate variability 2.3 The Little Kangerluluup lake system T. Guillemot et al. Lake Little Kangerluluup (60◦3803200 N; 45◦3801100 E; 10 ma.s.l.) is also a proglacial 10 lake, located close to Kangerluluup Qaqaa hill and Lake Kangerluluup, near the Tor- Title Page sukattak fjord (Fig. 1c). It is quite circular with a tiny surface of 6 ha and a maxi- Abstract Introduction mum depth of 6.4 m. Lake Little Kangerluluup is fed by only one major tributary and is drained directly into the Torsukattak fjord by one outlet (Fig. 1c). Like Lake Qallimiut, Conclusions References its catchment is composed of granites (geological survey of Denmark and Greenland; 2 Tables Figures 15 http://www.geus.dk).