HR: 09:00h
AN: U31A-04 INVITED     [Abstracts]
TI: What can we learn from corals about low-frequency (decadal-secular) climate variability?
AU: * Cole, J E
EM: jecole@email.arizona.edu
AF: University of Arizona - Geosciences Department, 1040 E. 4th St, Tucson, AZ 85721, United States
AU: Ault, T R
EM: tault@email.arizona.edu
AF: University of Arizona - Geosciences Department, 1040 E. 4th St, Tucson, AZ 85721, United States
AU: Barnett, H
EM: hbarnett@email.arizona.edu
AF: University of Arizona - Geosciences Department, 1040 E. 4th St, Tucson, AZ 85721, United States
AB: Corals offer excellent reconstructions of interannual climate anomalies in the tropical oceans, but many studies have raised questions about their ability to faithfully track decadal variability and long-term trends. Yet resolving such variability in the tropical oceans is crucial for questions of climate dynamics and identification of anthropogenic impacts. Understanding the mechanisms of this low-frequency variability is critical because it provides a basis for prediction, and because such variability may interact with higher-frequency or secular patterns to alter predictability and produce unexpected climate extremes. Long-term climate variations and trends in the tropics have the potential to impact climate globally through altered atmospheric circulation, systems such as ENSO and the monsoons, and teleconnections to extratropical climates. The 20th-century record of instrumental observations is too short to address these issues with confidence. Paleoclimate records from corals can contribute to this effort, if subtle signals of low-frequency change can be disentangled from sources of noise. Here we present several approaches to this issue. First, a synthesis of 23 coral geochemical records suggests that a common pattern of decadal variation can be extracted from these records. This pattern closely resembles a 20th century mode identified from instrumental data, but our analysis indicates that this mode was significantly stronger in the 19th century (explaining nearly half the deseasonalized variance). This mode resembles ENSO in spatial pattern, implicating equatorial dynamics. Second, we explore longer-term modes in individual records and identify an interval in the 17th century during which several global and Pacific-sensitive records appear to follow a bidecadal beat. Finally, we analyze the warming/freshening trends apparent in nearly all coral climate records and assess their correlation to local SST and salinity changes. The amplitude of trends at most sites is near or beyond what can be explained with existing instrumental records, but the lack of local salinity records on reefs, coupled with potential changes in the isotopic content of precipitation, means that these trends cannot yet be dismissed as biological artifacts.
DE: 4513 Decadal ocean variability (1616, 1635, 3305, 4215)
DE: 4916 Corals (4220)
DE: 4922 El Nino (4522)
DE: 4954 Sea surface temperature
SC: Union [U]
MN: 2007 Joint Assembly