HR: 17:30h
AN: PP54A-07    [Abstracts]
TI: High Frequency Climate Variability Over the Last 1400 Years in the Gulf of Mexico
AU: * Richey, J N
EM: jrichey@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St Petersburg, FL 33701 United States
AU: Flower, B P
EM: bflower@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St Petersburg, FL 33701 United States
AU: Poore, R Z
EM: rpoore@usgs.gov
AF: U.S. Geological Survey, 600 4th St South, St Petersburg, FL 33701 United States
AU: Quinn, T M
EM: tquinn@marine.usf.edu
AF: College of Marine Science, University of South Florida, 140 7th Ave South, St Petersburg, FL 33701 United States
AB: Low latitude, late Holocene climate is highly dynamic; multiple records show high frequency oscillations and distinct climate events such as the Medieval Warm Period (MWP) and Little Ice Age (LIA). The use of combined δ¹⁸O and Mg/Ca enables the determination of the relative contributions of changes in SST and changes in the hydrologic cycle, especially in regions linked to continental climate such as the Gulf of Mexico (GOM). Paired δ¹⁸O and Mg/Ca analyses of the planktonic foraminifer Globogerinoides ruber (white variety) from a Pigmy Basin box core (age control provided by 7 AMS radiocarbon dates) indicate persistent high frequency climatic variability in the GOM overprinted on an apparent MWP- LIA oscillation. The change in δ¹⁸O_calcite between the LIA (~1500_AD-1850_AD) and MWP (~600_AD -1400_AD) is equivalent to 0.4 ‰, with a positive 0.2‰ departure from the modern values during the LIA, and a negative 0.2‰ departure during the preceding MWP. The combined δ¹⁸O and Mg/Ca analysis indicates that the shift in δ¹⁸O_calcite is dominated by changes in salinity, with minimal SST variability during this period. Mg/Ca derived SSTs vary by a magnitude of <0.5 °C between the MWP/LIA. The calculated residual δ¹⁸O_seawater yields a 0.2-0.3‰ shift between the LIA and MWP, indicating a significant increase in salinity from the MWP to the LIA. Spectral analysis of δ¹⁸O_calcite and corresponding faunal data (% G. sacculifer) indicates a significant periodicity of ~200 years, close to the 208-year cycle in atmospheric ¹⁴C production and suggestive of a solar forcing mechanism. A higher frequency peak occurs in both proxies at a period of ~60-75 years. This may relate to the AMO signal evident in the instrumental record of SST in the North Atlantic.
DE: 4271 Physical and chemical properties of seawater
DE: 4825 Geochemistry
DE: 4835 Marine inorganic chemistry (1050)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005