The next thing that needs to be done is AMS dating. This will give us a time scale and will allow us to determine whether the samples are from the beginning of the transition from late Neoglacial to Medieval Warm Period or from the end.
Another big question that remains to be answered is the cause of the increase in variability. Is this an effect of salinity fluctuations caused by prolonged drought or decadal-scale temperature fluctuations? To answer this, we will be testing the Mg/Ca ratio of the aragonite. The Mg/Ca ratio is fractionated by the clam in the same way that oxygen isotopes are fractionated. However, because magnesium and calcium concentrations in the ocean are constant, changes in the Mg/Ca ratio reflect pure temperature variation. Using this method we will be able to separate the effects of salinity and temperature on the oxygen isotope ratio of the clamshell.
Finally, we would like to examine seasonality at Cedar Key during this time period. Yearly temperatures currently range from about 10 LC to 32 LC. ENSO has a large effect on winter weather in Florida. An ENSO warm event generally brings wet and cool conditions to Florida. Therefore, ENSO events should appear in the oxygen isotope ratios of the clamshells. We will do sampling at monthly resolution on some of the clamshells to determine if there was a difference in seasonality and the state of ENSO in Florida during the transition to the Medieval Warm Period.