کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6428487 | 1634737 | 2015 | 10 صفحه PDF | دانلود رایگان |
- We reconstruct sea surface temperatures from the Monte dei Corvi reference section.
- U37Kâ² - derived temperatures indicate warmth of over 10â°C above modern prior to 8 Ma.
- We find extreme and a secular drastic cooling between 6.7-7.4 Ma.
- We link temperature, aridity and terrestrial evolutionary events between 12-6 Ma.
In the Late Miocene, grasslands proliferated, succulent plants diversified in the mid-latitudes, and the desert-like conditions appeared in the Sahara. Despite this major environmental change on land, the coeval deep-sea oxygen isotope record does not provide evidence for significant high latitude cooling or continental ice growth, making it difficult to relate widespread terrestrial environmental change to global climatic changes. A U37Kâ² -derived sea surface temperature (SST) reconstruction spanning 13 to 6 Ma from uplifted hemipelagic sediments in Northern Italy provides the first continuous mid-latitude temperature record with which to compare the evolution of aridity and biotic events at similar latitudes in Northern Africa and Pakistan. Between 13 and 8.8 Ma, Mediterranean SST lay near the upper limit of the alkenone temperature proxy (â¼28â°C), exceeding modern SST at the site by as much as 10â°C. Throughout the record, sapropel layers correspond to local SST maxima, suggesting that Late Miocene hydrological conditions in the Mediterranean responded to insolation forcing via mechanisms similar to those documented for the Plio-Pleistocene. Mediterranean SST cooled rapidly beginning at â¼8 Ma, with an episode of intense cooling to â¼19â°C between 7.2 Ma and 6.6 Ma, followed by a rebound to â¼25â°C preceding the Messinian Salinity Crisis at 5.9 Ma. These observations establish, for the first time, a direct relationship between increasing aridity in the Northern hemisphere mid-latitudes and significant cooling. Evidently, this cooling was not accompanied by significant growth in continental ice volume. The extreme warmth and subsequent cooling of the Mediterranean Sea are not well-represented in current Late Miocene climate models, which our results suggest underestimate regional warmth prior to the Late Miocene cooling. Evidence of secular cooling during the Late Miocene gives new support to the much-debated link between a possible decline in atmospheric CO2 levels and Late Miocene changes in vegetation on land.
Journal: Earth and Planetary Science Letters - Volume 419, 1 June 2015, Pages 71-80