Details

Autor(en) / Beteiligte

• Ruddiman, William F.

Titel

Cold climate during the closest Stage 11 analog to recent Millennia

Ist Teil von

• Quaternary science reviews, 2005-05, Vol.24 (10), p.1111-1121

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2005

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The early part of marine isotopic Stage 11 near 400,000 years ago provides the closest analog to Holocene insolation levels of any interglaciation during the era of strong 100,000-year climatic cycles. The CH 4 concentration measured in Vostok ice fell to ∼450 ppb, and CO 2 values to ∼250 ppm. These natural decreases contrast with the increases in recent millennia and support the early anthropogenic hypothesis of major gas emissions from late-Holocene farming. During the same interval, δD values fell from typical interglacial to nearly glacial values, indicating a major cooling in Antarctica early in Stage 11. Other evidence suggests that new ice was accumulating during the closest insolation analog to the present day: a major increase in δ 18O atm at Vostok, a similar increase in marine δ 18O values, and re-initiation of ice rafting in the Nordic Sea. The evidence permits extended (>20,000 year) intervals of Stage 11 interglacial warmth in the Antarctic and North Atlantic, yet it also requires that this warmth ended and a new glacial era began when insolation was most similar to recent millennia. The Holocene CO 2 anomaly was produced only in part by direct anthropogenic emissions; over half of the anomaly resulted from the failure of CO 2 values to fall as they had during previous interglaciations because of natural responses, including a sea-ice advance in the Antarctic and ice-sheet growth in the northern hemisphere.