to increased evaporation and decreased precipitation associated with a warmer climate. Mono Lake reveals the climate variation on 3 different time scales: Dansgaard-Oeschger (repeats every 1,000 years), Heinrich (varying repetition), and Milankovich (repeats every 10,000 years). Dansgaard-Oeschger From the compilation of δ18O data over the past 51,000 years from lakes throughout the Great Basin, including Pyramid Lake, Summer Lake, Owens Lake, and Mono Lake, it has been observed that changes in lake level can be correlated to Dansgaard-Oeschger events. The δ18O records from these lakes showed oscillations in δ18O compositions of carbonates from these four lakes. Oscillation between high δ18O and low δ18O reflected cold/dry (low lake level with low precipitation) and warm/wet (high lake level with high precipitation) respectively. Read more about these isotopic effects in the Lake Level History section. Furthermore, total organic carbon (TOC) of the sediments from Pyramid Lake and Owens Lake were inversely correlated with δ18O and showed the same oscillations. TOC is often an indicator of the degree of biological productivity in a lake. This would suggest that high productivity correlated with a warm/wet climate at Mono Lake, while low productivity correlated with a cold/dry climate at Mono Lake. The timing of these oscillations matched the timing of Dansgaard-Oeschger events of the GISP2 core from 46 - 27 ka. Minima in δ18O and maxima in TOC correlated with 11 different Dansgaard-Oeschger events. Dansgaard-Oeschger events are fluctuations in δ18O records from ice cores that repeat every 1,000 years. They are thought to be related to global climatic events. However, the exact causes for these fluctuations are still unresolved. Heinrich events The lake level history of 36,000 years was investigated through correlations between δ18O records, radiocarbon dating, and paleomagnetic secular variation from Mono Lake sediments as described in the Lake Level History section. Peaks in the δ18O records of Mono Lake sediments correlated with 3 Heinrich events known from the sea cores of the North Atlantic. Heinrich events occurred when massive numbers of icebergs broke off from the ice sheets and fell into the North Atlantic. These Heinrich events have been observed to correlate with peaks in δ18O compositions of carbonates globally. This pattern would generally indicate a global drop in temperature and a rising ice-volume. As water vapor moves from the equator to the poles, 18O is preferentially precipitated compared to 16O. When the water precipitates at the poles, it has a very depleted δ18O