Oldest lake in Europe unravels 1.3 million years of climate history

Scientists found out what the climate was like over 1.3 million years ago in the mid and north Mediterranean after studying Lake Ohrid, Europe's oldest lake. The results of their research are published in the scientific journal Nature.

"We discovered a teleconnection between the African monsoon and winter precipitation in the Mediterranean region, so between tropical climate systems and rainfall in the mid-latitudes thousands of kilometers away," Dr. Alexander Francke of the University of Wollongong stated.

The research was led by Dr. Hendrik Vogel from the University of Bern and Associate Professor Bernd Waner from the University of Cologne.

Together with Dr. Francke, the team studied sediments from the lake's area that's 245 m (804 feet) deep. They drilled 568 m (1 863 feet) into the bed of Lake Ohrid. The water is located on the border of Albania and North Macedonia.

Examinations revealed that Lake Ohrid first occurred 1.36 million years ago. The sediment data displayed a great increase in winter precipitation on warm weather in the northern Mediterranean region. The climate in the said area is defined by wet winters and dry summers, which is linked to its interaction with tropical African seasons.

"We discovered a teleconnection between the African monsoon and winter precipitation in the Mediterranean region, so between tropical climate systems and rainfall in the mid-latitudes thousands of kilometers away," Dr. Francke added.

He further explained, "This climate system would be fairly stable during the summer and autumn until the temperatures decrease in winter and cold air from the north causes the whole system to become unstable and this low-pressure system moves eastwards towards the Balkan Peninsula and promotes rainfall in the winter months,"

This new discovery will be used to improve the previous models and look for more insights as to what the Mediterranean conditions could possibly be in the future.

Reference:

"Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years" – Bernd Wagner, Hendrik Vogel, Alexander Francke et al. – Nature 2019 

Abstract

Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance.

Featured image credit: Albinfo