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| -Signs, Portents, and the Weather- |
| Surprise - Earth's Climate Is Seesawing, According To Climate Researchers |
| 2007-05-01 |
| During the last 10,000 years climate has been seesawing between the North and South Atlantic Oceans. As revealed by findings presented by Quaternary scientists at Lund University, Sweden, cold periods in the north have corresponded to warmth in the south and vice verse. These results imply that Europe may face a slightly cooler future than predicted by IPCC, the Intergovernmental Panel on Climate Change. The research group, currently consisting of Svante Björck, Karl Ljung and Dan Hammarlund, has retrieved cores of lake sediments and peat along a north-south transect of Atlantic islands and adjacent land areas: Greenland, Iceland, Faroes, Azores, Tristan da Cunha, Isla de los Estados, and the Antarctic Peninsula. Based on detailed analyses of geochemistry, mineral magnetism and pollen content, hitherto unknown details of Atlantic climate dynamics have been resolved. Extensive radiocarbon dating and rapid sedimentation rates in the terrestrial deposits allow a much higher temporal resolution of the data than provided by marine sediment cores. Our records reflect details of the climatic evolution in the Atlantic region since the end of the last Ice Age to the present day. We would have liked to compare our results to similar data sets from other parts of the South Atlantic, but no other records provide the same degree of resolution, says Professor Björck. After the end of the last Glacial both Hemispheres became warmer as a result of melting ice sheets, but during the last 9000 years we can identify a persistent "seesaw" pattern. When the South Atlantic was warm it was cold in the North Atlantic and vice versa. This is most certainly related to large-scale ocean circulation in the Atlantic Ocean. The main current system - "the Great Ocean Conveyor" - is driven by sinking of dense, relatively cold and salty water in the northern North Atlantic. This results in southward-flowing deep-water that is replaced by warm surface water brought to high northern latitudes from the tropics and ultimately from the South Atlantic, says Svante Björck, and continues: The deep-water formation in the north is dependent on cooling of surface water with a high salt content. If sufficiently large amounts of fresh water are supplied to the North Atlantic, such as from melting ice-sheets or major increases in precipitation, the deep-water formation, and hence the transport of warm surface water from the south, may cease or at least decrease substantially. This is known to have happened repeatedly during the present Interglacial (the warm period since the last Ice Age). Minor disturbances have taken place in recent time, such as the Great Salt Anomaly in the 1970s, which seriously affected the cod population around the Faroe Islands. Our results from Nightingale Island in the Tristan da Cunha island group, between South Africa and Argentina, for the first time give evidence of warming of the South Atlantic associated with cooling in the north. This is a major breakthrough in palaeoclimate research. In agreement with most other climate researchers, the Lund group is not concerned about a complete shut-down of the Gulf Stream as envisioned in the apocalyptic film "The day after tomorrow". However, future warming induced by anthropogenic greenhouse-gas emissions may influence the system. We don’t know with certainty what will happen. Some attempts at measuring ocean currents suggest a recent weakening of the Gulf Stream, and the transport of heat to the North Atlantic region may well decrease in the future as a result of increased precipitation. Such a scenario might lead to less warming in Europe than predicted by the IPCC, but we will probably not face an arctic climate, summarizes Svante Björck. |
| Posted by:Cleash Omereter2552 |
| #4 2x4...I understand that you have to be careful mixing plate tectonics and global climate as they are related. However, it is unclear where Gondwana was in relation to the equator, etc., etc. As you so aptly point out there are countless of middle latitude examples of a topsey-turvey biosystem that is directly related to the climate. The bottom line: We are still a long ways from equilibrium exiting the last ice age. Throw in the measured variation in the solar contstant...and there is your "climate change". |
| Posted by: anymouse 2007-05-01 23:44 |
| #3 Why is there evidence of subtropical climate under the Antarctic Ice Cap? Anymouse, that is an entirely different question. Kinda relates to a question why there are remnants of coral reefs at Spitsbergen. No, not that old as mythical Gondwana, quite fresh, < 50kya (the results of dating vary from 50kya to 3.5kya). |
| Posted by: twobyfour 2007-05-01 17:49 |
| #2 Don't confuse infidel facts with Gore-facts, anymouse. It confuses the followers of Gaia and makes them grumpy. |
| Posted by: DarthVader 2007-05-01 15:29 |
| #1 I say again for the 100th time...Most atmospheric scientists are employed by the US government. Government policy forbids government workers from publicly deviating from the government's position or directives. And, that includes the climate change debate...unless we are doing applied or theoretical research. The majority of government atmospheric scientists are familiar with, or well-versed in the climate change arguments, and are skeptical at best. You will not see their names in a magazine, or the paper, or TV debating the issue with moonbats or zeolts on either side of the issue. I will also restaste what I say to folks who ask about the certainty of man-induced climate change: "Why do you think they call it Greenland? If Global Circulation Models that support inundation of the coastal regions by the end of the 21st century due to the melting of polar ice are so good, why do short term atmospheric models that are orders of magnitude more sophisticated go unstable after 10 days? Why is there evidence of subtropical climate under the Antarctic Ice Cap?" |
| Posted by: anymouse 2007-05-01 12:58 |