Hypothesized Link Between Glacial/Interglacial Atmospheric CO2 Cycles and Storage/Release of CO2-Rich Fluids From Deep-Sea Sediments - Abrupt Climate Change: Mechanisms, Patterns, and Impacts - page 122

Hypothesized Link Between Glacial/Interglacial Atmospheric CO 2 Cycles
and Storage/Release of CO 2 -Rich Fluids From Deep-Sea Sediments

Lowell Stott

Department of Earth Sciences, University of Southern California, Los Angeles, California, USA

Axel Timmermann

International Pacific Research Center, SOEST, University of Hawaii, ' iatM ā noa, Honolulu, Hawaii, USA

During the last glacial termination, the rise in atmospheric pCO 2 was accompa-
nied by a precipitous drop in surface ocean

14 C that cannot be explained by
changes in 14 C production alone and therefore appears to require a

Δ

14 C-

flux of

14 C excursion is
hard to reconcile with an ocean-only mechanism of CO 2 regulation. Here we
explore the possibility that hydrothermal sources of CO 2 contributed to glacial/
interglacial CO 2 variability and to the

depleted carbon into the surface ocean. The magnitude of this Δ

14 C variations during the last deglaciation.
We hypothesize that as the ocean cooled during glaciations CO 2 -hydrate stability
expanded upward to shallower depths and over a broader region of the sea

Δ

oor,

flux of 14 C-depleted CO 2 into the ocean from sediment reservoirs that
blanket active vents throughout the ocean. Conversely, as the oceans warmed
during deglaciation, the CO 2 -hydrate stability horizon deepened and caused a
transient release of 14 C-depleted CO 2 from the sediment reservoirs. Using a
transient glacial-interglacial simulation conducted with the Earth system model of
LOVECLIM, we estimate that ~3°C temperature increase at intermediate water
depths in the Paci

reducing the

c during the last deglaciation would have been large enough to
lower the hydrate stability horizon by several hundred meters and signi cantly

reduce the areal extent of sea oor where hydrate was stable. This hypothesis would

explain why 14 C ages of abyssal water masses were not anomalously old during the
last glacial and why there was a large radiocarbon activity (

14 C) anomaly during

Δ

the last deglaciation at intermediate (500 - 700 m) water depths.

1. INTRODUCTION

Among of the most striking aspects of Earth ' s natural long-
term climate behavior are the abrupt terminations of ice ages
and their close temporal relationship to rising concentrations
of atmospheric CO 2 (Plate 1). The last ice age ended between
19 and 10 kyr B.P., accompanied by an ~80 ppm rise in