Reconstruction of paleotemperatures in the Northwest Pacific over the past 3000 years from δ~(18)O values of the micro-bivalvia Carditella iejimensis found in a submarine cave

摘要

We measured the δ~(18)O values of the whole shells of the cavernicolous micro-bivalvia Carditella iejimensis obtained from sediments within a submarine cave (31m water depth) at Ie Island (Okinawa Island, Japan) in the subtropical Northwest Pacific. Our results show no significant millennial-scale trend in the δ~(18)O record, implying that both springtime temperature and the δ~(18)O of sea water at 30 m depth around the Okinawa Islands have been stable for the past 3000 years at values similar to those of today. Moreover, we found one exceptionally light δ~(18)O value from specimens spanning the past 250 years. The δ~(18)O-derived temperature represents a departure of 2.1 ℃ from the average value for the past 250 years, being equal to the departure recorded during unusually high temperatures in the spring of 1998. This finding may imply that such high springtime sea surface temperature has been a rare event over the past 3000 years.