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 accurately1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles2,3 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.
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Data are available from the Pangaea database (https://doi.pangaea.de/10.1594/PANGAEA.896848); links to the individual datasets are provided within this dataset. Data used for LOVECLIM are available at https://climatedata.ibs.re.kr/grav/data/loveclim-784k. Additional data are available upon request made to T.F. (email@example.com).
Model data produced by the LOVECLIM simulations are available through the data centre of the IBS Center for Climate Physics (https://climatedata.ibs.re.kr/grav/data/loveclim-784k).
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The Hydrobiological Institute in Ohrid (S. Trajanovski and G. Kostoski) and the Hydrometeorological Institute in Tirana (M. Sanxhaku and B. Lushaj) provided logistic support for site surveys and the scientific drilling campaign. Drilling was carried out by Drilling, Observation and Sampling of the Earth’s Continental Crust (DOSECC). A. Skinner provided logistic and technical advice before and during the drilling operation. The Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO) drilling project was funded by the International Continental Scientific Drilling Program (ICDP), the German Ministry of Higher Education and Research, the German Research Foundation, the University of Cologne, the British Geological Survey, the INGV and CNR (both Italy), and the governments of the republics of North Macedonia and Albania. V. Scao collected the V5 tephra, which was 40Ar/39Ar dated with funding from the LEFE ‘INTERMED’ grant (CNRS-INSU) to S.N.
The authors declare no competing interests.
Peer review information Nature thanks Simon Blockley, Dirk Verschuren and Zhongshi Zhang for their contribution to the peer review of this work.
Extended data figures and tables
Extended Data Fig. 2 Correlation of tephra layers at the DEEP site with tephra layers from mid-distal records.
a–e, Bi-oxide plots of CaO versus FeOtotal (a), CaO versus Al2O3 (b), CaO versus TiO2 (c), Na2O versus K2O (d) and a total alkali versus silica diagram92 (e) show the correlation of OH-DP-2669 with the tephra layers SC1-35.30/SUL2-1/V5 and the differences to the Parmenide ash. f–j, Bi-oxide plots of CaO versus FeOtotal (f), CaO versus Al2O3 (g), CaO versus TiO2 (h), Na2O versus K2O (i) and total alkali versus silica diagram (j) show the correlation of OH-DP-2898 with tephra SUL2-22 and the differences to SUL2-23, SUL2-27, SUL2-31, V4, V3 and the Pitagora ash. Error bars for the data of the Parmenide ash indicate the standard deviation54. Tephra ages, geochemical data, tephrostratigraphic discussion and references are provided in Extended Data Tables 1, 2 and the Methods. Source Data
Extended Data Fig. 3 Correlation of tephra layers OH-DP-2669 and V5 based on trace element compositions.
Trace element data of OH-DP-2669 support the correlation with tephra V5a/b52. a, Th versus Y. b, Th versus Zr. c, Th versus Nb. d, Th versus La. e, Th versus Ce. f, Th versus Pr. g, Th versus Nd. h, Th versus Gd. i, Th versus Yb. Error bars for the data of OH-DP-2669 represent uncertainties at a 95% confidence interval. ppm, parts per million.
Extended Data Fig. 4 Lake Ohrid LOVECLIM simulation data and sedimentary palaeoclimate and palaeoenvironment proxies.
a, Simulated surface-air temperature (SAT) for the Lake Ohrid grid cell from the LOVECLIM simulation. b, Simulated precipitation amount for the Lake Ohrid grid cell from the LOVECLIM simulation. c, Lake Ohrid TOC concentrations. d, Lake Ohrid δ13C endogenic calcite in parts per thousand relative to VPDB. e, Lake Ohrid δ18O endogenic calcite in parts per thousand relative to VPDB. f, Lake Ohrid relative sedimentary quartz content. g, Lake Ohrid K intensities in kilo counts and displayed using a 11-point (pt) running mean. h, Lake Ohrid ratio of Ca/K intensities displayed using a 11-point running mean. i, Lake Ohrid Ca intensities in kilo counts and displayed using a 11-point running mean. j, Lake Ohrid TIC concentrations. k, Percentages of deciduous oak pollen at Lake Ohrid. l, Percentages of arboreal pollen excluding Pinus pollen at Lake Ohrid. Red and white diamonds indicate the position of radiometrically dated tephra layers, blue and white diamonds the position of reversals of Earth’s magnetic field in the Lake Ohrid sediment record. b, d, e, j–l, Data are the same as in Fig. 2. Source Data
a, b, Continuous wavelet transform on the percentage of TIC (a) and percentage of deciduous oak pollen (DOP; b) from Ohrid DEEP. Yellow, highest power; red, lowest power; grey contour, cone of influence; black contour, 5% significance level82 against red-noise background corrected for autocorrelation81,93. c, d, Least squares regression (red line) between band pass-filtered 18–25-kyr-old component of percentage of TIC (c) and the percentage of DOP against precession at a 1-kyr resolution (d). Blue lines indicate 95% bootstrapped (n = 1,999) confidence intervals. Significant negative responses to precession are seen in both proxies, with a stronger response in DOP. Partial datasets for the intervals <0.78 Myr ago, <1.2 Myr ago, <1.36 Myr ago indicate persistence of the correlation despite changes in lake ontogeny and global scale changes in boundary conditions. e, f, PLSR using TIC and DOP as predictive variables and LOVECLIM temperature (e) and precipitation (f) simulations as observations demonstrate significant explanatory power by the proxies on the simulation time series, particularly for precipitation. PLSR was performed using SIMCA 14 (Sartorius Stedim Biotech), using 1.4–33-kyr bandpass-filtered data to accommodate for slight age offsets between proxy and simulation data. Source Data
a, Ages of sapropels and humid phases in the eastern Mediterranean based on Soreq Cave speleothem δ18O data and U/Th chronology71. b, Simulated precipitation amount for the Lake Ohrid grid cell from the LOVECLIM simulation. c, Percentage of deciduous oak pollen at Lake Ohrid. d, Lake Ohrid TIC concentrations. e, Chinese Speleostack25 δ18O in parts per thousand relative to VPDB. Red and white diamonds indicate the position of radiometrically dated tephra layers in the Lake Ohrid record. The chronology of the MIS 5 interval in the Lake Ohrid DEEP site record is based on a previous study94. Source Data
Extended Data Fig. 7 Simulated Lake Ohrid precipitation for full-forcing run and sensitivity simulations.
a, Lake Ohrid precipitation (cm yr−1) for full-forcing simulation (black) and a simulation using only orbital forcing under a warm background climate (red). b, Black line as in a and a simulation using only orbital forcing under a cold background climate (blue). c, Black line as in a and a simulation using full-forcing except for a constant preindustrial Northern Hemisphere (NH) ice sheet. d, Black line as in a and a simulation using full-forcing except for constant preindustrial GHG concentrations. Note that the sensitivity simulations only cover the past 408 kyr (see Methods for details on the sensitivity simulations). Source Data
Extended Data Fig. 8 Mean seasonal cycle of precipitation in the Lake Ohrid grid cell from LOVECLIM model simulation and NOAA reanalysis data.
a, Reconstructed precipitation (cm yr−1) for the Lake Ohrid reanalysis grid cell. Data are based on monthly means. Dashed line indicates two standard deviations above the mean. b, Composite anomalies of 850 hPa geopotential height (m) associated with Lake Ohrid precipitation maxima shown in a and referring to the months shown in c. c, Monthly distribution of precipitation maxima shown in a. d, Mean seasonal cycle of simulated Lake Ohrid precipitation (cm yr−1) for all model years (green) and model years with annual mean precipitation exceeding two standard deviations (magenta). See also Fig. 3a. e, Mean seasonal cycle of Lake Ohrid precipitation (cm yr−1) derived from NOAA reanalysis data (blue) and simulated for the period from 1 kyr ago to present (red). The annual means were removed for better comparison and are provided in the panel. Source Data