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Abrupt changes in atmospheric methane at the MIS 5b–5a transition
Author(s) -
Grachev Alexi M.,
Brook Edward J.,
Severinghaus Jeffrey P.
Publication year - 2007
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2007gl029799
Subject(s) - ice core , deglaciation , methane , groenlandia , geology , climatology , atmospheric sciences , environmental science , holocene , ice sheet , chemistry , geomorphology , oceanography , organic chemistry
New ice core analyses show that the prominent rise in atmospheric methane concentration at Dansgaard‐Oeschger event 21 was interrupted by a century‐long 20% decline, which was previously unrecognized. The reversal was found in a new ∼100‐year resolution study of methane in the GISP2 ice core, encompassing the beginning of D‐O event 21, which also corresponds to the transition from MIS 5b to 5a. Although a corresponding reversal (within age uncertainty) is observed in climate proxies measured in GISP2 ice, including δ 18 O ice , electrical conductivity, light scattering, and several ions, this feature has not been discussed previously. Abrupt changes in methane are paralleled by changes in δ 15 N of trapped air, a quantity that reflects local temperature change at Greenland summit. The reversal described here supports the hypothesis that climate can be unstable during major transitions, as was previously described for the last deglaciation.