However, two lines of evidence indicate that at Steel Lake, evaporative 18O enrichment related to aridity was the dominant control. First, the d18O values of water samples from the epilimnion and hypolimnion of Steel Lake were 8.7 and 10.7%, respectively, in July 2001 (Figure 1d). The elevated d18O value of the epilimnetic water resulted from evaporative 18O enrichment, suggesting that Steel  Lake is sensitive to evaporation;In particular, the most severe historic drought events in north-central Minnesota, the 1988 drought [Trenberth et al., 1988] and 1930s Dust Bowl [Worster, 1979], are recorded by the heaviest d18O values at Steel Lake

Tian, Jian , Nelson, David M. , Hu, Feng Sheng

Possible linkages of late-Holocene drought in the North American midcontinent to Pacific Decadal Oscillation and solar activity

Tian, J., Nelson, D. M. and Hu, F. S.: Possible linkages of late-Holocene drought in the North American midcontinent to Pacific Decadal Oscillation and solar activity, Geophysical Research Letters, 33(23), doi:10.1029/2006gl028169, 2006.

d18O (LS06TIST): interpretation3_scope: '' has been replaced by 'isotope'
d18O (LS06TIST): interpretation4_scope: '' has been replaced by 'isotope'

Kiel automated device for isotope ratio mass spectrometry on a Finnigan Delta XL mass ratio spectrometer.

Chara encrustations, ostracodes, gastropod and mollusk shell fragments and the <125-mm fraction of marl sediment from selected intervals of the core

Bulk sediment samples were taken from core C/E for isotope analyses at 0.5-cm increments for the uppermost 16.5 cm (32 field-extruded samples; Glew, 1988; Glew et al., 2001), at 1-cm increments from 16.5-cm depth to the White River Ash at 64-cm depth, and at 2-cm increments from 64- to 144-cm depth for a total of 121 samples. The bulk sediment samples were wet sieved through nested screens (63, 125, 250-mm), collected separately and freeze dried. At least five individual Chara stem encrustations (1?3 mm each in length) were picked from the dried fractions, examined for purity, homogenized and sub- sampled for CO2 extraction