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Atmospheric Δ 14 C reduction in simulations of Atlantic overturning circulation shutdown
Author(s) -
Matsumoto Katsumi,
Yokoyama Yusuke
Publication year - 2013
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1002/gbc.20035
Subject(s) - teleconnection , slowdown , thermohaline circulation , climatology , seesaw molecular geometry , atmosphere (unit) , environmental science , shutdown of thermohaline circulation , north atlantic deep water , ocean current , atmospheric circulation , atmospheric sciences , oceanography , geology , geography , meteorology , physics , el niño southern oscillation , neutrino , nuclear physics , political science , law
A rapid reduction in the Atlantic meridional overturning circulation (AMOC) can significantly disrupt the global heat transport and likely triggered abrupt climate change during the last glacial cycle. A slowdown in AMOC has long been assumed to inhibit the exchange of carbon between the atmosphere and the deep ocean and thus cause radiocarbon ( 14 C), which is produced in the atmosphere, to accumulate in the atmosphere. Indeed previous model studies have demonstrated that a reduction in AMOC leads to higher atmospheric 14 C abundance (Δ 14 C). However, this seems inconsistent with the observed rise in atmospheric p CO 2 during Heinrich 1 and the Younger Dryas stadial events and the emerging view that this CO 2 rise resulted from the deep ocean venting “old” carbon. Using an Earth system model, we offer an alternative scenario that AMOC slowdown and an accompanying dynamical response in the south (i.e., the bipolar seesaw) can in fact lead to a decline in atmospheric Δ 14 C. This decline is realized in the model when the bipolar seesaw and thus the flux of old carbon from the Southern Ocean are sufficiently large so as to overcome the accumulation of 14 C in the atmosphere as AMOC is reduced. The bipolar seesaw we describe invokes an oceanic teleconnection, whereby a freshwater perturbation in the North Atlantic drives a southern Δ 14 C response, but this does not necessarily preclude an atmospheric teleconnection.