Lake Ohrid, located on the border between the republics of Albania and North Macedonia, is the oldest lake in Europe and one of the most biodiverse in the world. An international team of scientists, including Dr Jack Lacey and Prof Melanie Leng from the British Geological Survey, have investigated extensive sediment cores from the lake as part of a transdisciplinary deep drilling project. The team have recently published their results in the journal Nature. In this blog, Jack introduces the research project and describes their findings...
The Scientific Collaboration on Past Speciation Conditions in Lake Ohrid project (or SCOPSCO for short) brought together over 50 scientists from 13 different countries to determine the age and origin of the lake and investigate the climate and environmental change history of the Mediterranean region. The project started 15 years ago with preliminary site surveys. In 2013 a deep drilling campaign took place in co-operation with the International Continental scientific Drilling Program (ICDP). Over 2.1 km of sediment core was recovered from five drill sites; the deepest core taken in the centre of the lake resulted in a continuous 584-m-long composite sequence with over 99 % sediment recovery. The upper 447 m of this profile comprised fine grain muds and contained no hiatuses, indicating continuous lake conditions. Chronological data demonstrate that this uninterrupted record spans the last 1.36 million years.
Analysis of the sediment cores took five years – there was a lot of material. The team used a variety of independent analytical techniques on the cores to provide an extended and robust climate history for the Mediterranean region. At the British Geological Survey, we used chemical data from the sediment, measuring the oxygen and carbon (isotope) content of carbonate minerals, to help better understand past changes in rainfall.
Our isotope results, in combination with other geochemical datasets from collaborators, show that there was significantly higher winter rainfall in the northern Mediterranean region during warmer intervals (known as interglacials). These intervals are characterised by the Earth having higher CO2 levels, less polar ice and large seasonal differences in the amount of solar energy reaching the Earth’s surface. We also found a strong connection between Mediterranean winter rainfall and African monsoon strength throughout the record. This indicates that variations in solar energy are a key driver of the African monsoon and also have a dominant control on rainfall variability in the Mediterranean over the last 1.4 million years.
The long and continuous nature of the Ohrid record allowed us to compare our data with climate model outputs, which provided information about the main drivers of climate variability. Current projections for future changes in Mediterranean winter rainfall are ambiguous and so our data will help to improve climate model outputs and constrain future climate scenarios for the region. Any changes in winter rainfall will impact water availability across the Mediterranean and could have strong social and economic implications for this densely populated region.
The next phase of the SCOPSCO project is to assess the influence of geological events, climate and environmental changes on the unique biodiversity of Lake Ohrid and to investigate whether these have shaped speciation and evolution in the lake.
References:
Paper: Wagner et al. 2019. Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature 573, 256-260.
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| ICDP barge and drill rig platform used to recover sediment cores from the bottom of Lake Ohrid (image: Niklas Leicher) |
The Scientific Collaboration on Past Speciation Conditions in Lake Ohrid project (or SCOPSCO for short) brought together over 50 scientists from 13 different countries to determine the age and origin of the lake and investigate the climate and environmental change history of the Mediterranean region. The project started 15 years ago with preliminary site surveys. In 2013 a deep drilling campaign took place in co-operation with the International Continental scientific Drilling Program (ICDP). Over 2.1 km of sediment core was recovered from five drill sites; the deepest core taken in the centre of the lake resulted in a continuous 584-m-long composite sequence with over 99 % sediment recovery. The upper 447 m of this profile comprised fine grain muds and contained no hiatuses, indicating continuous lake conditions. Chronological data demonstrate that this uninterrupted record spans the last 1.36 million years.
Analysis of the sediment cores took five years – there was a lot of material. The team used a variety of independent analytical techniques on the cores to provide an extended and robust climate history for the Mediterranean region. At the British Geological Survey, we used chemical data from the sediment, measuring the oxygen and carbon (isotope) content of carbonate minerals, to help better understand past changes in rainfall.
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| Sorting the cores back on shore (image: Stefan Schorr) |
Our isotope results, in combination with other geochemical datasets from collaborators, show that there was significantly higher winter rainfall in the northern Mediterranean region during warmer intervals (known as interglacials). These intervals are characterised by the Earth having higher CO2 levels, less polar ice and large seasonal differences in the amount of solar energy reaching the Earth’s surface. We also found a strong connection between Mediterranean winter rainfall and African monsoon strength throughout the record. This indicates that variations in solar energy are a key driver of the African monsoon and also have a dominant control on rainfall variability in the Mediterranean over the last 1.4 million years.
 |
| Jack processing sub-samples of the core at BGS, ready for isotope analysis |
The long and continuous nature of the Ohrid record allowed us to compare our data with climate model outputs, which provided information about the main drivers of climate variability. Current projections for future changes in Mediterranean winter rainfall are ambiguous and so our data will help to improve climate model outputs and constrain future climate scenarios for the region. Any changes in winter rainfall will impact water availability across the Mediterranean and could have strong social and economic implications for this densely populated region.
The next phase of the SCOPSCO project is to assess the influence of geological events, climate and environmental changes on the unique biodiversity of Lake Ohrid and to investigate whether these have shaped speciation and evolution in the lake.
References:
Paper: Wagner et al. 2019. Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years. Nature 573, 256-260.
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