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Tomas Næraa

Tomas Naeraa

Researcher

Tomas Næraa

Holocene Hydrographic Variations From the Baltic-North Sea Transitional Area (IODP Site M0059)

Author

  • S. Ni
  • N. B. Quintana Krupinski
  • J. Groeneveld
  • A. S. Fanget
  • M. E. Böttcher
  • B. Liu
  • M. Lipka
  • K. L. Knudsen
  • T. Naeraa
  • M. S. Seidenkrantz
  • H. L. Filipsson
Show all

Summary, in English

Deoxygenation affects many continental shelf seas across the world today and results in increasing areas of hypoxia (dissolved oxygen concentration ([O2]) <1.4 ml/L). The Baltic Sea is increasingly affected by deoxygenation. Deoxygenation correlates with other environmental variables such as changing water temperature and salinity and is directly linked to ongoing global climate change. To place the ongoing environmental changes into a larger context and to further understand the complex Baltic Sea history and its impact on North Atlantic climate, we investigated a high accumulation-rate brackish-marine sediment core from the Little Belt (Site M0059), Danish Straits, NW Europe, retrieved during the Integrated Ocean Drilling Program (IODP) Expedition 347. We combined benthic foraminiferal geochemistry, faunal assemblages, and pore water stable isotopes to reconstruct seawater conditions (e.g., oxygenation, temperature, and salinity) over the past 7.7 thousand years (ka). Bottom water salinity in the Little Belt reconstructed from modeled pore water oxygen isotope data increased between 7.7 and 7.5 ka BP as a consequence of the transition from freshwater to brackish-marine conditions. Salinity decreased gradually (from 30 to 24) from 4.1 to ~2.5 ka BP. By using the trace elemental composition (Mg/Ca, Mn/Ca, and Ba/Ca) and stable carbon and oxygen isotopes of foraminiferal species Elphidium selseyensis and E. clavatum, we identified that generally warming and hypoxia occurred between about 7.5 and 3.3 ka BP, approximately coinciding in time with the Holocene Thermal Maximum (HTM). These changes of bottom water conditions were coupled to the North Atlantic Oscillation (NAO) and relative sea level change.

Department/s

  • Centre for Environmental and Climate Science (CEC)
  • Quaternary Sciences
  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • Lithosphere and Biosphere Science

Publishing year

2020-02-01

Language

English

Publication/Series

Paleoceanography and Paleoclimatology

Volume

35

Issue

2

Document type

Journal article

Publisher

Wiley-Blackwell

Topic

  • Oceanography, Hydrology, Water Resources
  • Geology

Keywords

  • foraminifera
  • Holocene Thermal Maximum
  • LA-ICP-MS
  • NAO
  • Skagerrak
  • trace elements

Status

Published

Project

  • Tracing marine hypoxic conditions during warm periods using a microanalytical approach
  • Tracing hypoxia during warm periods in the Baltic Sea region - using synchrotron X-ray spectroscopy and plasma analytical methods

ISBN/ISSN/Other

  • ISSN: 2572-4517