Paper No. 13
Presentation Time: 11:15 AM
A PUERTO RICO SPELEOTHEM AND INFERRED DRYING OF THE EASTERN CARIBBEAN CLIMATE IN THE PAST 800 YEARS
MILLER, Thomas E.1, WINTER, A.
2, STOTT, Lowell
3, KUSHNIR, Yochanan
4, SINHA, Ashish
5, TIMMERMANN, Axel
6, JURY, Mark
2, GALLUP, C.
7, CHENG, Hai
8 and EDWARDS, R. Lawrence
8, (1)Department of Geology, University of Puerto Rico, Mayaguez, PR 00681, (2)Department of Marine Sciences, University of Puerto Rico, Mayagüez, Mayagüez, PR 00681, (3)Earth Science, Univ of southern california, 3651 Trousdale Pkwy, Los Angeles, CA 90089, (4)Lamont-Doherty Earth Observatory of Columbia University, 61 Route 9W, Palisades, NY 10964, (5)Dept. of Earth System Science, California State University, Dominguez Hills, 1000 E Victoria St, Carson, CA 90747, (6)International Pacific Research Center, SOEST, University of Hawaii, Manoa, Honolulu, HI 96822, (7)Dept. of Geological Sciences, University of Minnesota Duluth, Duluth, MN 55812, (8)Department of Earth Sciences, University of Minnesota, 310 Pillsbury Dr. SE, Minneapolis, MN 55455, thomase.miller@upr.edu
The active stalagmite PDR-1 from a Puerto Rico cave has provided the first reconstruction of rainfall variability for the past 800 years of the western tropical Atlantic. The δ
18O of speleothem calcite was analyzed at annual resolution from 1850 to the collection in June, 2006, and every five years from AD 1200-1850. The δ
18O of Puerto Rico primarily varies with changes in the amount of summer rain (85% of the annual total), and suggests an overall trend of declining rainfall and warmer temperatures for the past eight centuries in the eastern Caribbean. The speleothem data set can be subdivided into three segments (the period from 1850 to the present which tracks the Atlantic Multidecadal Oscillation (AMO), the middle segment co-varies well with the tree-ring based extension of the AMO back to 1597, and lastly, the independent speleothem data of AD 1200-1600). Given the first two correlations, we suggest that the speleothem δ
18O-based rainfall record from Puerto Rico extends the history of the AMO to the 12th century.
The collection was from a large cave (Cueva Perdida, 18.3°N, 350 m a.s.l.), in an isolated chamber >360 m from an entrance; subsequent to removal, a data logger onsite recorded very stable temperatures of 220C and 100% relative humidity during the period of monitoring. The 15 cm stalagmite was cut along its vertical growth axis, polished, and samples of the upper 3 cm were collected for 230Th dating. Using a magnetic sector ICPMS, seven dates were obtained in stratigraphic order. An eighth date of ~10.5 kaBP was determined for the base. Samples for δ18O analysis were milled at intervals of 0.05mm along the axis.
These δ18O(VPDB) values varied between -1.5 to -3.5 ‰ , steadily rising from AD 1200-1600, dropping abruptly from then to 1700, rising again to 1850, and oscillating since then. During this same period, at the other end of the Caribbean rainfall also appears to have decreased in Belize, but stayed more or unless unchanged in the dry Yucatan to the north.
