|
|
|
|
|
| Eldevik, Tor; Risebrobakken, Bjorg; Bjune, Anne E.; Andersson, Carin; Birks, H. John B.; Dokken, Trond M.; Drange, Helge; Glessmer, Mirjam S.; Li, Camille; Nilsen, Jan Even O.; Ottera, Odd Helge; Richter, Kristin; Skagseth, Oystein. |
| The understanding of climate and climate change is fundamentally concerned with two things: a well-defined and sufficiently complete climate record to be explained, for example of observed temperature, and a relevant mechanistic framework for making closed and consistent inferences concerning cause-and-effect. This is the case for understanding observed climate, as it is the case for historical climate as reconstructed from proxy data and future climate as projected by models. The present study offers a holistic description of northern maritime climate from the Last Glacial Maximum through to the projected global warming of the 21st century in this context. It includes the compilation of the most complete temperature record for Norway and the Norwegian Sea... |
| Tipo: Text |
Palavras-chave: LGM-to-future North Atlantic; Nordic seas; And Arctic Climate Marine Terrestrial Reconstruction Observations Climate model Temperature Thermohaline circulation. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00289/40031/38847.pdf |
| |
|
|
| Dokken, Trond M.; Nisancioglu, Kerim H.; Li, Camille; Battisti, David S.; Kissel, Catherine. |
| Dansgaard-Oeschger (D-O) cycles are the most dramatic, frequent, and wide-reaching abrupt climate changes in the geologic record. On Greenland, D-O cycles are characterized by an abrupt warming of 105 degrees C from a cold stadial to a warm interstadial phase, followed by gradual cooling before a rapid return to stadial conditions. The mechanisms responsible for these millennial cycles are not fully understood but are widely thought to involve abrupt changes in Atlantic Meridional Overturning Circulation due to freshwater perturbations. Here we present a new, high-resolution multiproxy marine sediment core monitoring changes in the warm Atlantic inflow to the Nordic seas as well as in local sea ice cover and influx of ice-rafted debris. In contrast to... |
| Tipo: Text |
Palavras-chave: D-O cycles; Nordic seas; Marine sediment core; Greenland ice core; Abrupt changes; Sea ice. |
| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00264/37490/35779.pdf |
| |
|
|
| Berben, Sarah M.p.; Dokken, Trond M.; Abbott, Peter M.; Cook, Eliza; Sadatzki, Henrik; Simon, Margit H; Jansen, Eystein. |
| Understanding the dynamics that drove past abrupt climate changes, such as the Dansgaard-Oeschger (DO) events, depends on combined proxy evidence from disparate archives. To identify leads, lags and synchronicity between different climate system components, independent and robust chronologies are required. Cryptotephrochronology is a key geochronological tool as cryptotephra horizons can act as isochrons linking disparate and/or distant records. Here, we investigated marine sediment core MD99-2284 from the Norwegian Sea to look for previously identified Greenland ice core cryptotephra horizons and define time-parallel markers between the archives. We explored potential secondary transport and depositional mechanisms that could hamper the isochronous... |
| Tipo: Text |
Palavras-chave: Quaternary; Paleoclimatology; Paleoceanography; North Atlantic; Sedimentology; Marine cores; Ice cores; Cryptotephrochronology; DO-Events; Synchronization. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00622/73391/72606.pdf |
| |
|
|
| Sadatzki, Henrik; Maffezzoli, Niccolò; Dokken, Trond M.; Simon, Margit H; Berben, Sarah M. P.; Fahl, Kirsten; Kjær, Helle A.; Spolaor, Andrea; Stein, Ruediger; Vallelonga, Paul; Vinther, Bo M.; Jansen, Eystein. |
| Constraining the past sea ice variability in the Nordic Seas is critical for a comprehensive understanding of the abrupt Dansgaard-Oeschger (D-O) climate changes during the last glacial. Here we present unprecedentedly detailed sea ice proxy evidence from two Norwegian Sea sediment cores and an East Greenland ice core to resolve and constrain sea ice variations during four D-O events between 32 and 41 ka. Our independent sea ice records consistently reveal a millennial-scale variability and threshold response between an extensive seasonal sea ice cover in the Nordic Seas during cold stadials and reduced seasonal sea ice conditions during warmer interstadials. They document substantial and rapid sea ice reductions that may have happened within 250 y or... |
| Tipo: Text |
Palavras-chave: Sea ice; Nordic Seas; Dansgaard-Oeschger events; Abrupt climate change. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00659/77066/78374.pdf |
| |
|
|
| Tisserand, Amandine A.; Dokken, Trond M.; Waelbroeck, Claire; Gherardi, Jeanne Marie; Scao, Vincent; Fontanier, Christophe; Jorissen, Frans. |
| Benthic foraminiferal Mg/Ca has been shown to have great potential as a proxy for reconstructing deep water temperatures. However, the exact relationship between Mg uptake in benthic foraminifera and temperature is still ambiguous, and further exploration and refinement is much needed to reduce uncertainties associated with the method. Here, we present new core-top Mg/Ca data from benthic foraminiferal species from the lower part of the thermocline in the western tropical Atlantic (northern Brazilian margin). This area is unusual in that the changes in carbonate chemistry along the transect are very small, making it an ideal region for isolating and studying the role of temperature in the incorporation of Mg into the benthic shells. Our results show that... |
| Tipo: Text |
Palavras-chave: Benthic foraminiferal Mg; Ca; Intermediate water temperature; Equatorial thermocline; Western tropical Atlantic Ocean; Core-tops. |
| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00181/29191/27596.pdf |
| |
|
|
| Sadatzki, Henrik; Dokken, Trond M.; Berben, Sarah M. P.; Muschitiello, Francesco; Stein, Ruediger; Fahl, Kirsten; Menviel, Laurie; Timmermann, Axel; Jansen, Eystein. |
| The last glacial period was marked by pronounced millennial-scale variability in ocean circulation and global climate. Shifts in sea ice cover within the Nordic Seas are believed to have amplified the glacial climate variability in northern high latitudes and contributed to abrupt, high-amplitude temperature changes over Greenland. We present unprecedented empirical evidence that resolves the nature, timing, and role of sea ice fluctuations for abrupt ocean and climate change 32 to 40 thousand years ago, using biomarker sea ice reconstructions from the southern Norwegian Sea. Our results document that initial sea ice reductions at the core site preceded the major reinvigoration of convective deep-water formation in the Nordic Seas and abrupt Greenland... |
| Tipo: Text |
|
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00484/59606/62620.pdf |
| |
|
|
| Rutledal, Sunniva; Berben, Sarah M.p.; Dokken, Trond M.; Van Der Bilt, Willem G.m.; Cederstrøm, Jan Magne; Jansen, Eystein. |
| Geochemically distinct volcanic ash (tephra) deposits are increasingly acknowledged as a key geochronological tool to synchronize independent paleoclimate archives. Recent advances in the detection of invisible (crypto) tephra have led to the ongoing establishment, development and integration of regional tephra lattices. These frameworks offer an overview of the spatial extent of geochemically characterized tephra from dated eruptions – a valuable tool for precise correlation of paleorecords within these areas. Here, we harness cryptotephra analysis to investigate the occurrence of two well-known tephra markers from the Last Glacial Period (i.e. FMAZ II-1 (26.7 ka b2k) and NAAZ II (II-RHY-1) (55.3 ka b2k)), in marine sediment cores from the Nordic,... |
| Tipo: Text |
Palavras-chave: Tephrochronology; Cryptotephra Tephrostratigraphy; Tephra isochrons; FMAZ II; NAAZ II; Geochemistry; Paleoceanography; Marine sediment cores Quaternary; North Atlantic Ocean. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00614/72659/71665.pdf |
| |
|
|
| Meland, Marius Y.; Dokken, Trond M.; Jansen, Eystein; Hevroy, Kjersti. |
| Twenty benthic oxygen isotope records from different water depths in the Nordic seas and the North Atlantic are compared. During the Last Glacial Maximum, brine formation on continental shelves produced Brine Shelf Water (BSW), sinking below 1500 m in the Nordic seas. Open- ocean convection in the Nordic seas produced Glacial North Atlantic Intermediate Water (GNAIW). GNAIW overflowed the Greenland-Scotland Ridge and entrained depths above and at least partly below 2000 m in the North Atlantic. During the early deglaciation, BSW-enriched intermediate water masses in the Nordic seas were formed. These overflowed the Greenland-Scotland Ridge and influenced the North Atlantic intermediate and deepwater masses. In the Bolling-Allerod ( BA), open-ocean... |
| Tipo: Text |
|
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34873/33188.pdf |
| |
|
|
|
