. Bulletins of American paleontology. 274 Bulletin 361 100- 110- 120- Annual ,3q_| Rainfall (cm) MO- ISO- 160- 170 Russell Bank Core 19B Ostracode Mg/Ca - Based Salinity vs. Rainfall SM-5 SM-4 SM-3 SM-1 -50. Rainfall Russell Salinity â 70 â 60 ^0 Salinity (PPt) [-30 20 hio 0 -| . 1 : 1 1 1 1 1 . 1 . 1 . 1 . 1 , 1 , 1 , 1 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Text-figure 9.âOstracode Mg/Ca-based salinity estimates for Russell core 19B and 5-year running mean of annual rainfall. Salinity derivation discussed in text. SM designates intervals of relative salini
. Bulletins of American paleontology. 274 Bulletin 361 100- 110- 120- Annual ,3q_| Rainfall (cm) MO- ISO- 160- 170 Russell Bank Core 19B Ostracode Mg/Ca - Based Salinity vs. Rainfall SM-5 SM-4 SM-3 SM-1 -50. Rainfall Russell Salinity â 70 â 60 ^0 Salinity (PPt) [-30 20 hio 0 -| . 1 : 1 1 1 1 1 . 1 . 1 . 1 . 1 , 1 , 1 , 1 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year Text-figure 9.âOstracode Mg/Ca-based salinity estimates for Russell core 19B and 5-year running mean of annual rainfall. Salinity derivation discussed in text. SM designates intervals of relative salinity maximum. A comparison of the Mg/Ca record from the Russell core to the rainfall record reveals many similarities (Text-figure 8). For example, the rainfall data indicate that since the late 1950's there have been 3 quasi-de- cadal oscillations in precipitation over southern Flori- da. While the amplitude correspondence varies, within the resolution of sediment chronology, the three rain- fall oscillations are matched one-for-one by oscilla- tions in ostracode Mg/Ca ratios. Over this time inter- val, peaks in Mg/Ca occur during dry intervals in the early 1960"s, mid-to-late 1970's, and the late 1980"s, all periods of known hypersalinity within Florida Bay. The decadal-scale correlation between rainfall and Mg/Ca persists in the earlier part of the records as well. Based on the rainfall record, this was a period of low amplitude rainfall oscillations relative to the last 50 years, a pattern that also appears in the Mg/Ca record. Thus, Mg/Ca and rainfall show a correspon- dence over multi-decadal timescales. In addition to the longer-term correlation, it also ap- pears that single-year climate events may be recorded in the Mg/Ca record. For example, four of the extreme minima over the last century closely correspond with years when the El Nino southern oscillation index (SOI) was strongly negative (Text-fig. 8). Typically, south Florida receives unusually high dry-
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