Tuesday, March 31, 2009

Pliocene Warm Period

Greatly Expanded Tropical Warm Pool and Weakened Hadley Circulation in the Early Pliocene in Science.
The Pliocene warm interval has been difficult to explain. We reconstructed the latitudinal distribution of sea surface temperature around 4 million years ago, during the early Pliocene. Our reconstruction shows that the meridional temperature gradient between the equator and subtropics was greatly reduced, implying a vast poleward expansion of the ocean tropical warm pool. Corroborating evidence indicates that the Pacific temperature contrast between the equator and 32°N has evolved from 2°C 4 million years ago to 8°C today. The meridional warm pool expansion evidently had enormous impacts on the Pliocene climate, including a slowdown of the atmospheric Hadley circulation and El NiƱo–like conditions in the equatorial region. Ultimately, sustaining a climate state with weak tropical sea surface temperature gradients may require additional mechanisms of ocean heat uptake (such as enhanced ocean vertical mixing).

Orbital resonance and Solar cycles

Orbital resonance and Solar cycles
A detailed analysis of the couplings between the orbits of the planets and possible relationships with solar activity and the earth's climate. Nice graphics.

Is the Milky Way "Rotation Curve" Real?

Indications of an Unmodelled Component in Spectrographic Measurements of Local Stars
The Milky Way's rotation curve appears to be flat, based on the measured doppler shifts of interstellar gas. In contrast, the authors find that the rotation curve of the motions of local stars is not flat. Is the explanation an unmodelled component to the spectrographic measurements?