Figure 2

(a) Ice sheet reconstructions from three different sources with the volume of ice (plain curves, left axis) and associated meltwater flux (dashed curves, right axis) potentially draining to the Caspian Sea and Black Sea catchment. “A”¹³ and “1”¹² represent meltwater-driven flux reconstructions from the Caspian Sea to the Black Sea. (b) Black Sea level (right axis, m, relative to modern sea level) and associated volume changes (left axis, km³) deduced from the Black Sea’s water budget with FIS meltwater input as shown in panel a), and the regional water flux P–E (precipitation-minus-evaporation) from two transient simulations of MIROC4m and Trace-21 ka. The water volume is expressed as the complementary volume needed to reach the Bosphorus sill at − 37 m, the level necessary for the Black Sea to outflow to the Mediterranean. The lowest BSL at the LGM is estimated to be – 105 m^29,30 and the total volume for outflowing to occur is 29,675 km³ (light blue horizontal patch). Superimposed are BSL reconstructions by Lericolais et al.²⁹, Genov³⁰ and Aksu and Hiscott¹¹. The reconstruction by Aksu and Hiscott (2022) suggests a Black Sea outflowing from 17.2 to 15.7 ka over the uppermost “Pleistocene delta Δ2” (− 55 m) as inferred from seismic reflection. (c) Black Sea freshwater outflowing (red, blue, and green) over the Bosphorus sill, as a result of (a) and (b). The black plain line marked with “B” represents an estimation (in mSv) by Chepalyga¹³. Black dots (marked with “a” and “b”) represent other two estimations for 15 ka at the Bosphorus Strait³¹. The horizontal plain lines represent the chronology reported in previous studies for Black Sea outflowing to the Marmara Sea (purple) and the Aegean Sea (orange). Blue patches represent the scenarios of the present study carrying out hosing experiments with a regional oceanic model: “4mSvFIS” (12,614 km³ of additional freshwater over 100 years) and “17mSvFIS” (53,611 km³ over 100 years).