 |
| Titel |
Abrupt sea surface pH change at the end of the Younger Dryas in the central sub-equatorial Pacific inferred from boron isotope abundance in corals (Porites) |
| VerfasserIn |
E. Douville, M. Paterne, G. Cabioch, P. Louvat, J. Gaillardet, A. Juillet-Leclerc, L. Ayliffe |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 7, no. 8 ; Nr. 7, no. 8 (2010-08-16), S.2445-2459 |
| Datensatznummer |
250004932
|
| Publikation (Nr.) |
 copernicus.org/bg-7-2445-2010.pdf |
|
|
|
|
|
| Zusammenfassung |
| The "δ11B-pH" technique was applied to
modern and ancient corals Porites from the sub-equatorial Pacific areas (Tahiti and
Marquesas) spanning a time interval from 0 to 20.720 calendar years to
determine the amplitude of pH changes between the Last Glacial Period and
the Holocene. Boron isotopes were measured by Multi-Collector – Inductively
Coupled Plasma Mass Spectrometry (MC-ICPMS) with an external reproducibility
of 0.25‰, allowing a precision of about ±0.03 pH-units for pH values
between 8 and 8.3. The boron concentration [B] and isotopic composition of
modern samples indicate that the temperature strongly controls the partition
coefficient KD for different aragonite species. Modern coral δ11B
values and the reconstructed sea surface pH values for different
Pacific areas match the measured pH expressed on the seawater scale and
confirm the calculation parameters that were previously determined by
laboratory calibration exercises. Most ancient sea surface pH
reconstructions near Marquesas are higher than modern values. These values
range between 8.19 and 8.27 for the Holocene and reached 8.30 at the end of
the last glacial period (20.7 kyr BP). At the end of the Younger Dryas
(11.50±0.1 kyr BP), the central sub-equatorial Pacific experienced
a dramatic drop of up to 0.2 pH-units from the average pH of 8.2 before and
after this short event. Using the marine carbonate algorithms, we
recalculated the aqueous pCO2 to be 440±25 ppmV at around
11.5 kyr BP for corals at Marquesas and ~500 ppmV near Tahiti where it
was assumed that pCO2 in the atmosphere was 250 ppmV. Throughout the
Holocene, the difference in pCO2 between the ocean and the atmosphere at
Marquesas (ΔpCO2) indicates that the surface waters behave as a
moderate CO2 sink or source (−53 to 20 ppmV) during El Niño-like
conditions. By contrast, during the last glacial/interglacial transition,
this area was a marked source of CO2 (21 to 92 ppmV) for the
atmosphere, highlighting predominant La Niña-like conditions. Such
conditions were particularly pronounced at the end of the Younger Dryas with
a large amount of CO2 released with ΔpCO2 of +185±25 ppmV.
This last finding provides further evidence of the marked changes in the
surface water pH and temperature in the equatorial Pacific at the Younger
Dryas-Holocene transition and the strong impact of oceanic dynamic on the
atmospheric CO2 content. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|