Variation of deep water formation in the Labrador Sea over the last glacial cycle (130 KY) and the future climate model projections
| dc.contributor.author | Cottet, Melanie | en_US |
| dc.date.accessioned | 2024-08-13T18:12:06Z | |
| dc.date.available | 2024-08-13T18:12:06Z | |
| dc.date.copyright | 2002 | en_US |
| dc.date.issued | 2002 | |
| dc.degree.department | School of Earth and Ocean Sciences | |
| dc.degree.level | Master of Science M.Sc. | en |
| dc.description.abstract | A major issue in paleoclimatology is understanding the exact relation between the gradual variations in solar forcing and geological records of rapid climate changes. The formation of North Atlantic Deep Water (NADW) tightly governs the present global climate and is believed to play a major role in this relation. In this thesis the variation of N ADW formation from the last interglacial period (the Eemian - 125 kbp) to global warming projections is investigated using numerical simulations conducted with the UVic Earth System Climate Model. The results are compared with proxy paleo-reconstructions. The NADW is currently composed of two water masses: 1- the deep Denmark Strait Overflow Water (DSOW) originating from the Nordic Seas and represented in the model by convection in the Irminger Sea, 2- the intermediate Labrador Sea Water (LSW), seasonally renewed by winter convection. In the different simulations it is seen that there is no convection in the Labrador Sea during the Eemian and the Last Glacial Maximum (LGM: 21 kbp) in agreement with paleo-reconstructions. The inception of modern-like circulation at 8 kbp proposed by these reconstructions is not captured by the model unless the fresh water forcing from ice sheet melting is applied in a transient simulation. This raises implications concerning the applicability of the use of equilibrium simulations in representing changing climates. In global warming projections, the formation of LSW stops as CO2 rises, and recovers afterward. On the other hand, in all simulations the convection permanently remains active in the eastern North Atlantlic, its latitude depending on the sea ice edge position. The convection occurs through the cooling of the North Atlantic Drift water. The Irminger convection site is in direct contact with the North Atlantic Drift and is therefore relatively stable. The LSW formation on the other hand takes place in a confined environment far from this source and is very sensitive to variations in surface fresh water fluxes. These variations can be induced by external forcings : CO2 concentration and orbital geometry, as well as ice sheet melting. It is seen that the intensity of the thermohaline circulation is highly dependent on LSW formation which hence plays a major role in the short term climate variations. This encourages further monitoring in the Labrador Sea as a measure of the oceanic response to anthropogenic warming. | |
| dc.format.extent | 79 pages | |
| dc.identifier.uri | https://hdl.handle.net/1828/17533 | |
| dc.rights | Available to the World Wide Web | en_US |
| dc.title | Variation of deep water formation in the Labrador Sea over the last glacial cycle (130 KY) and the future climate model projections | en_US |
| dc.type | Thesis | en_US |
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