ridges right, we can explore the sensitivity of these limbs to the same kind of salinity forcing. I predict that the Labrador Sea limb will respond on short time scales, and represent an important effect on the thermohaline circulation.

RIND: It has been suggested that at the time the last glacial cycle started there might actually have been a shutoff of the GIN seas component, while the Labrador Sea component continued.

GHIL: If North Atlantic Deep Water is formed by Arctic intermediate water, we need to know what controls the formation of the Arctic intermediate water so we can put it into our models.

LEHMAN: The convection and water formation at both levels seem to be responding to salinity forcing at the surface, but even if the forcing fails to drive convection there's enough water backed up behind the sills to keep overflowing. I know I've simplified by ignoring the wind-driven gyre, but things might be simpler in the Labrador Sea. It would be interesting to apply the same salinity forcing to it as to the Norwegian Sea, and see whether you get the climate vibration you might expect.

GROOTES: This morning almost everyone said that we have some evidence for a 10- or 20-year time scale change, but not a long enough record. I just wanted to mention that my Figure 4 definitely shows a fluctuation on that scale. The Greenland ice sheet serves as a high-resolution monitor for climate variability in the Greenland and North Atlantic area, and I think we ice-core people need to get together with the oceanographers and modelers to put this kind of proxy data to better use.

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