An important characteristic of Mono Lake is that it is a closed lake, meaning it has no outflow. Water can only escape the lake if it evaporates or is lost to groundwater. This may cause closed lakes to become very saline. The reconstruction of historical Mono Lake levels through carbon and oxygen isotopes have also revealed a correlation with well-documented changes in climate.
In the recent past, Earth experienced periods of increased glaciation known as ice ages. This geological period of ice ages is known as the Pleistocene, which lasted until ~11 ka. Lake levels in Mono Lake can reveal how the climate fluctuated. For example, during the cold climate of the Pleistocene the lake level was higher because there was less evaporation and more precipitation. Following the Pleistocene, the lake level was generally lower due to increased evaporation and decreased precipitation associated with a warmer climate.
The lake level has fluctuated during the Holocene, since the end of the ice ages. The Holocene high point is at elevation , reached in approximately 1820 BCE. The low point before modern diversions is at elevation , reached in 143 CE. The lowest modern level due to diversions is at , reached in 1980.