Holocene Ocean Variability
High sedimentation rate deep-sea sediment cores can provide high-resolution records of surface ocean variability at decadal-century scales over past millennia to complement tree-ring and other high-resolution proxies. Several prior studies have noted that climate oscillations detected in may terrestrial archives such as the Little Ice Age and Medieval Climate Anomaly are also observed in ocean sediment records (see record below from ODP Site 658 off NW Africa and Bermuda; Keigwin et al., 1996; deMenocal et al., 2001; Bond et al., 1997, 2001).
Reliable calendar age control can be problematic due to unacceptably large dating uncertainties associated with analytical error and reservoir age uncertainties. A promising approach for assigning accurate calendar ages for deep-sea sediment records employs continuous, high-precision 14C dating that resolves the multidecadal 14C production variations (plateaux) associated with solar variability modulation of cosmogenic nuclide production. Sedimentation rates at ODP Site 1055 (NW Atlantic, Blake Outer Ridge, 1800m) exceed 40 cm/ka, affording 50-year (2cm) sample resolution extending throughout the
Holocene. Continuous 14C dating over the last 1000 years resolve the multidecadal 14C plateaux associated with the Maunder, Sporer, Wolf, and Oort solar minima, thereby aligning the SST record with solar forcing.
Current research aims to apply this dating method to many sediment cores to address spatial and temporal changes in SSTs as well as reservoir age anomalies. Below are some recent high-resolution dates from ODP Site 1055 off the Carolina margin (raw 14C ages have been corrected for 400 year reservoir age only). Additional wiggle-matching to the INCAL calibration curve produces accurate calendar ages for latest Holocene deep-sea sediments.
Some papers on this topic
Yashuhara, M., Cronin, T. M., deMenocal, P. B., Okahashi, H., and Linsley, B. K. (2008). Abrupt climate change and collapse of deep-sea ecosystems. Proc. Nat. Acad. Sciences 105, 1556-1560.
Koutavas, A., deMenocal, P.B., Olive, G.C., Lynch-Steiglitz, J. Mid-Holocene ENSO attenuation and background La Niña conditions in the tropical Pacific Ocean. Geology, 34 (12), pp. 993-996, 2006.
Farmer, E.C., deMenocal, P.B., Marchitto, T.M. Holocene and deglacial ocean temperature variability in the Benguela upwelling region: Implications for low-latitude atmospheric circulation. Paleoceanography, 20, doi:10.1029/2004PA001049. 2005.
Jansen, E., deMenocal, P., Grousset, F. Holocene climate variability – a marine perspective. Quat. Sci. Rev, 23, pp.2061-2061. 2004.
Marchitto, T. M. and P. B. deMenocal. Late Holocene variability of upper North Atlantic Deep Water temperature and salinity. Geochemistry, Geophysics, Geosystems 4(12): 1100, doi 10.1029/2003GC000598. 2003.
deMenocal, P.B., Ortiz, J., Guilderson, T., Sarnthein, M. Coherent High- and Low-Latitude Climate Variability during the Holocene Warm Period. Science, 288 (5474), 2198-2202. 2000.
Bond, G., W. Showers, M. Cheseby, R. Lotti, P. deMenocal, P. Priori, H. Cullen, I. Hadjes, and E. Bonani, A pervasive, millennial-scale cycle in the North Atlantic Holocene and Late Glacial climates, Science, 278: 1257-1266, 1997.
Holocene Ocean Variability
8/1/09
Current understanding of natural climate variability derives from relatively short instrumental records, mostly from land-based data. Ocean sediment records can constrain decadal-century scale variability over past millennia. Reliable SST proxies and better age control remain key hurdles.
