For the last few thousand years, a large number of these
volcanic events have been dated by different methods
(Zielinski et al. 1994): either by counting the layers in sites
with a sufficiently high accumulation or through historical
writings, or by dating volcanic material near the volcano in
question, especially by the carbon-14 method applied to
biological debris (e.g., trees caught in the lava). Starting with
an approximate glaciological dating, these events can generally be identified by their intensity in the cores. They can
also allow two ice cores to be stratigraphically connected
(see Fig. 9.5).
Before the Holocene, only a few layers of ash (Fig. 9.6)
can be dated accurately. Chemical analysis of these ashes
enables unambiguous identification of the relevant volcanic
eruption. This signature can sometimes be connected to that
of the volcanic material located close to a volcano. This
volcanic material, in larger quantity, can be dated by conventional radiochronological methods.
In this way, a visible ash layer in the ice cores of Dome C
and Dome Fuji could be dated by an American team using
the argon/argon method (see Chap. 5) to date ash found near
the volcano (Mt Berlin, Antarctica; Narcisi et al. 2006). For
Greenland, notable volcanic horizons were identified that are
referred as: Saksunarvatn, Vedde, Fugloyarbanki, ‘33 ka
14 C’ and Z2. These horizons were dated by the carbon-14
method or by the argon/argon method (see Svensson et al.
2008 and included references for further detail).
Dansgaard-Oeschger Events
Dansgaard-Oeschger events (D-O) were identified for the
first time in Greenland ice cores and correspond to abrupt
changes in temperature during the last glacial period (see
§3.2, Chap. 4). Synchronous variations (within a few decades) were also observed in the atmospheric content of
methane (Severinghaus et al. 1998) measured in air bubbles
from both Antarctic and Greenland ice. These events can
therefore be dated by the Greenland cores which are relatively precisely dated through counting of the annual layers
(See Section “The Counting of Annual Layers”). This dating
can then be transferred to the Antarctic cores thanks to the
methane records.
The changes in climate associated with the
Dansgaard-Oeschger events, although their maximum
impact was probably at the level of the North Atlantic, are
visible in many locations on the planet, in other climate
Fig. 9.5 Sulfate profiles for the first tens of meters in two ice cores
from Eastern Antarctica: EDC (EPICA Dome C, bottom) and B32
(top), the latter located near the EDML site (EPICA Dronning Maud
Land). Several well-known eruptions can be identified. Moreover, these
volcanic profiles can be used to synchronize the ice cores between each
other. Adapted from Severi et al. (2007)
Fig. 9.6 Ash layer present at about 239 m in the core drilled at Talos
Dome (East Antarctica). Copyright F. Parrenin (frederic.parrenin@univ-grenoble-alpes.fr)
128
F. Parrenin
volcanic events have been dated by different methods
(Zielinski et al. 1994): either by counting the layers in sites
with a sufficiently high accumulation or through historical
writings, or by dating volcanic material near the volcano in
question, especially by the carbon-14 method applied to
biological debris (e.g., trees caught in the lava). Starting with
an approximate glaciological dating, these events can generally be identified by their intensity in the cores. They can
also allow two ice cores to be stratigraphically connected
(see Fig. 9.5).
Before the Holocene, only a few layers of ash (Fig. 9.6)
can be dated accurately. Chemical analysis of these ashes
enables unambiguous identification of the relevant volcanic
eruption. This signature can sometimes be connected to that
of the volcanic material located close to a volcano. This
volcanic material, in larger quantity, can be dated by conventional radiochronological methods.
In this way, a visible ash layer in the ice cores of Dome C
and Dome Fuji could be dated by an American team using
the argon/argon method (see Chap. 5) to date ash found near
the volcano (Mt Berlin, Antarctica; Narcisi et al. 2006). For
Greenland, notable volcanic horizons were identified that are
referred as: Saksunarvatn, Vedde, Fugloyarbanki, ‘33 ka
14 C’ and Z2. These horizons were dated by the carbon-14
method or by the argon/argon method (see Svensson et al.
2008 and included references for further detail).
Dansgaard-Oeschger Events
Dansgaard-Oeschger events (D-O) were identified for the
first time in Greenland ice cores and correspond to abrupt
changes in temperature during the last glacial period (see
§3.2, Chap. 4). Synchronous variations (within a few decades) were also observed in the atmospheric content of
methane (Severinghaus et al. 1998) measured in air bubbles
from both Antarctic and Greenland ice. These events can
therefore be dated by the Greenland cores which are relatively precisely dated through counting of the annual layers
(See Section “The Counting of Annual Layers”). This dating
can then be transferred to the Antarctic cores thanks to the
methane records.
The changes in climate associated with the
Dansgaard-Oeschger events, although their maximum
impact was probably at the level of the North Atlantic, are
visible in many locations on the planet, in other climate
Fig. 9.5 Sulfate profiles for the first tens of meters in two ice cores
from Eastern Antarctica: EDC (EPICA Dome C, bottom) and B32
(top), the latter located near the EDML site (EPICA Dronning Maud
Land). Several well-known eruptions can be identified. Moreover, these
volcanic profiles can be used to synchronize the ice cores between each
other. Adapted from Severi et al. (2007)
Fig. 9.6 Ash layer present at about 239 m in the core drilled at Talos
Dome (East Antarctica). Copyright F. Parrenin (frederic.parrenin@univ-grenoble-alpes.fr)
128
F. Parrenin