| Summary: | Shallower/deeper lake levels at Summer Lake, OR, coincide with colder/warmer air temperatures at millennial time scales throughout the northern hemisphere between the end of Heinrich Event 4 (~38 ka) and the end of the intensity low associated with the Mono Lake geomagnetic excursion (~34 ka). The new results are based on lake-level estimates from a new set of proxies and age control from an improved record of the Mono Lake excursion, a geomagnetic event that also appears in a Greenland ice core during a stadial interval from 34.833.8 ka. Colder temperatures at Summer Lake are indicated by the presence of the ostracode Cytherissa lacustris in intervals previously predicted to be associated with low lake levels. Lake level, as suggested by bulk grain size, grain size of the coarse fraction, and carbon/nitrogen (C/N) ratio, was shallower when C. lacustris was present. These results confirm those of earlier studies at Summer Lake and other Great Basin lakes in western North America with respect to the relationship between millennial-scale temperature changes throughout the northern hemisphere and the response of regional climate in western North America at semitropical latitudes.
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