Heinrich-Scale Climate Oscillations in the Northeast Pacific: Atmospheric Transmission or Pacific Thermohaline Circulation and Heat Transport?

A.C. Mix, N.G. Pisias, D.C. Lund (College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331; ph. 541-737-5212; Internet: mix@oce.orst.edu); P. Boden (Dept. of Geology and Geochemistry, Stockholm University, S-106 91 Stockholm, Sweden); S.W. Hostetler (USGS, 200 SW 35th St., Corvallis, OR 97333); P.U. Clark (Dept. of Geosciences, Oregon State University, Corvallis, OR 97331); M. Lyle (CGISS, Boise State University, Boise, ID)

Evidence from planktonic fauna, benthic stable isotopes, radiocarbon, and biogenic sediment composition in deep-sea cores with sedimentation rates of 10-20 cm/ka under the Northern California Current off Oregon reveal repeated millennial-scale climate oscillations over the past ~100 ka. Here, increased ventilation at water depths of 1000 to 3000 m is associated on millennial scales with surface-ocean warming.

Detailed radiocarbon chronologies of the late-glacial interval, as well as relationships of benthic d18O to planktonic faunas in the same samples suggest that NE Pacific warming and enhanced deep Pacific ventilation correlates to (or slightly lags) stadial cooling in the N Atlantic. During these intervals, the North Pacific may have produced deep and/or intermediate water, perhaps enough to transport oceanic heat northward and shift the position of the Polar Front zone in the NE Pacific. Ventilation of the deep Pacific from the south, either by enhanced formation of bottom water in the Southern Ocean, or wind-forced export of Pacific deep water, may contribute to ventilation of the deep N Pacific but would probably not affect upper ocean temperatures in the NE Pacific.

The NE Pacific data suggest diachronous registration of millennial scale climate events along the Pacific coast of North America, and perhaps between the NW and NE Pacific. The polar front in the Northeast Pacific influences the mean position of storms as they track into North America, and thus may affect the registration of millennial-scale climate oscillations on the continent. Establishing cause and effect demands a spatial array of sites with a chronologic framework precise enough to resolve this diachroneity, and to establish relationships between climate oscillations in the North Pacific and western North America to better-known events of the North Atlantic.