A continuous record of temperature evolution over a sequence of Dansgaard-Oeschger events during Marine Isotopic Stage 4 (76 to 62 kyr BP).

• Main Authors: A Landais, J M Barnola, V Masson-Delmotte, J Jouzel, J Chappellaz, N Caillon, C Huber, M Leuenberger, S J Johnsen, A
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2004
• Subjects: Greenland; Dansgaard-Oeschger events; North Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1081.8915; http://www.jerome-chappellaz.com/files/publications/a-continuous-record-of-temperature-evolution-over-a-sequence-of-dansgaard-oeschger-events-during-marine-isotopic-stage-4-76-to-62-kyr-bp-67.pdf

[1] Our knowledge of the temperature evolution over Greenland during Dansgaard-Oeschger events (DO) is currently qualitatively described through the water isotopic profile. Using two independent paleothermometry methods, one based on air isotopic measurements and the other on the combined measurements of water isotopes (dD and d 18 O), we show a complete and quantitative reconstruction of temperature at the NorthGRIP site over the period 76 to 62 kyr BP (DO 18, 19 and 20). We confirm that the associated warmings are larger than those conventionally depicted by the water isotopes (11°C, 16°C and 11°C for DO 18, 19 and 20). Secondly, we demonstrate that the relationship between temperature and d 18 O varies rapidly during the last glacial period, even over a DO. Finally, our temperature reconstruction over DO 19 agrees well with that predicted from simple climate models linking the DO to iceberg discharges. [2] The last glacial cycle was characterized by millenial scale climate fluctuations that have been documented in the North Atlantic region through numerous marine and continental records [3] Ice cores have already provided a wealth of information on DO in Greenland through the water isotopes for temperature changes, chemical records for atmospheric circulation and analysis of air bubbles for changes in greenhouse gases concentration. However, temperature reconstruction from water isotopes is subject to large biases mainly due to (i) the seasonality of the precipitation (i.e., periods without precipitation will not have their temperature recorded) 18 O through the deuterium excess parameter O), we need additional information to account for the influence of seasonality and possible variation of the vertical atmospheric temperature profile (the isotopic composition of the snow depends on the condensation temperature). [4] One elegant way to overcome those difficulties is to use the isotopic composition of the air trapped in ice, a method based on the thermal diffusion of gases (nitrogen and argon), which allows ...