Articles | Volume 13, issue 6
Biogeosciences, 13, 1801–1820, 2016

Special issue: Integrated perspectives on biological and geological dynamics...

Biogeosciences, 13, 1801–1820, 2016

Research article 24 Mar 2016

Research article | 24 Mar 2016

Northern Mediterranean climate since the Middle Pleistocene: a 637 ka stable isotope record from Lake Ohrid (Albania/Macedonia)

Jack H. Lacey1,2, Melanie J. Leng1,2, Alexander Francke3, Hilary J. Sloane2, Antoni Milodowski4, Hendrik Vogel5, Henrike Baumgarten6, Giovanni Zanchetta7, and Bernd Wagner3 Jack H. Lacey et al.
  • 1Centre for Environmental Geochemistry, School of Geography, University of Nottingham, Nottingham, NG7 2RD, UK
  • 2NERC Isotope Geosciences Facilities, British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
  • 3Institute of Geology and Mineralogy, University of Cologne, 50674 Cologne, Germany
  • 4British Geological Survey, Keyworth, Nottingham, NG12 5GG, UK
  • 5Institute of Geological Sciences & Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland
  • 6Leibniz Institute for Applied Geophysics, 30655 Hanover, Germany
  • 7Dipartimento di Scienze della Terra, University of Pisa, Pisa, Italy

Abstract. Lake Ohrid (Macedonia/Albania) is an ancient lake with unique biodiversity and a site of global significance for investigating the influence of climate, geological, and tectonic events on the generation of endemic populations. Here, we present oxygen (δ18O) and carbon (δ13C) isotope data from carbonate over the upper 243 m of a composite core profile recovered as part of the Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) project. The investigated sediment succession covers the past ca. 637 ka. Previous studies on short cores from the lake (up to 15 m, < 140 ka) have indicated the total inorganic carbon (TIC) content of sediments to be highly sensitive to climate change over the last glacial–interglacial cycle. Sediments corresponding to warmer periods contain abundant endogenic calcite; however, an overall low TIC content in glacial sediments is punctuated by discrete bands of early diagenetic authigenic siderite. Isotope measurements on endogenic calcite (δ18Oc and δ13Cc) reveal variations both between and within interglacials that suggest the lake has been subject to palaeoenvironmental change on orbital and millennial timescales. We also measured isotope ratios from authigenic siderite (δ18Os and δ13Cs) and, with the oxygen isotope composition of calcite and siderite, reconstruct δ18O of lake water (δ18Olw) over the last 637 ka. Interglacials have higher δ18Olw values when compared to glacial periods most likely due to changes in evaporation, summer temperature, the proportion of winter precipitation (snowfall), and inflow from adjacent Lake Prespa. The isotope stratigraphy suggests Lake Ohrid experienced a period of general stability from marine isotope stage (MIS) 15 to MIS 13, highlighting MIS 14 as a particularly warm glacial. Climate conditions became progressively wetter during MIS 11 and MIS 9. Interglacial periods after MIS 9 are characterised by increasingly evaporated and drier conditions through MIS 7, MIS 5, and the Holocene. Our results provide new evidence for long-term climate change in the northern Mediterranean region, which will form the basis to better understand the influence of major environmental events on biological evolution within Lake Ohrid.

Short summary
We use stable isotope data from carbonates to provide a palaeoenvironmental reconstruction covering the last 637 kyr at Lake Ohrid (FYROM/Albania). Our results indicate a relatively stable climate until 450 ka, wetter climate conditions at 400–250 ka, and a transition to a drier climate after 250 ka. This work emphasises the importance of Lake Ohrid as a valuable archive of climate change in the northern Mediterranean region.
Final-revised paper