 |
| Titel |
Abrupt temperature changes and contrasted hydrological responses during
Greenland Stadial 1 in northern Iberia |
| VerfasserIn |
Miguel Bartolomé, Ana Moreno, Carlos Sancho, Heather Stoll, Isabel Cacho, Christoph Spötl, R. Lawrence Edwards, Hai Cheng, John Hellstrom |
| Konferenz |
EGU General Assembly 2016
|
| Medientyp |
Artikel
|
| Sprache |
en
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250131885
|
| Publikation (Nr.) |
 EGU/EGU2016-12335.pdf |
|
|
|
|
|
| Zusammenfassung |
| Greenland Stadial 1 (GS-1) was the last of a long series of severe cooling episodes in the
Northern Hemisphere during the last glacial period, whose origin is attributed to the complex
interaction of intense weakening of the Atlantic Meridional Overturning Circulation,
moderate negative radiative forcing and an altered atmospheric circulation (Renssen et al.,
2015). As a result, marine and terrestrial records from the North Atlantic region indicate a
cooling of several degrees, being larger in high latitudes (up to 4˚ C) and diminishing
towards the southeast (0.5˚ C) (Heiri et al., 2014). Here, we present the first stalagmite record
that covers the entire GS-1 period in Southern Europe, providing an excellent and
independent chronological framework and a high-resolution climate reconstruction of this
event (Bartolomé et al., 2015). The stalagmite is from Seso Cave from the central Pyrenees
(42˚ 27′23.08′′N, 0˚ 02′23.18′′E, 794 m asl) where a 3-year monitoring survey, together
with the analyses of actively growing modern stalagmites, allows climate proxies in
stalagmites to be calibrated to the instrumental record. Thus, analysis of oxygen
isotopes in a modern stalagmite from Seso Cave suggests a strong dependence on air
temperature through its influence on rainfall δ18O, providing a reliable proxy for the
temperature evolution during GS-1. According to these calculations, the δ18O change
of 2.14‰ during GS-1 is considered to represent a 1.3 ˚ C drop of the annual
temperature.
Besides reflecting GS-1 cooling in the Pyrenees, the Seso Cave stalagmite is used here to
investigate the timing and forcing of a mid–GS-1 climate transition previously reported from
northern European records (Lane et al., 2012). δ13C and Mg/Ca of Seso samples
show higher values between 12,920 y b2k and 12,500 y b2k, a gradual decrease
until ca. 12,000 y b2k, and a period with lower values until the Holocene onset at
11,700 y b2k. This pattern, although still at low resolution due to a reduced growth
rate, is reproduced in two stalagmites more from Central Iberia (La Galiana Cave,
Soria province). Monitoring of Seso Cave shows low speleothem δ13C and Mg/Ca
values coinciding with increased infiltration into the cave as a result of a higher
precipitation-evaporation balance in the region. This is consistent with well-documented
processes by which slower drip rates enhance degassing and raise dripwater Mg/Ca ratios and
δ13C values. Therefore, these proxy data suggest a first phase of relatively drier
conditions until 12,500 y b2k and a progressive increase in humidity afterward. This
gradual transition from dry to wet conditions starting at 12,500 y b2k occurred
during a progressive warming of the subtropical Atlantic Ocean (Schmidt et al.,
2011) and a resumption of the Atlantic overturning circulation (Hughen et al., 2000)
while conditions in Greenland were still cold. This, therefore, demonstrates a rapid
coupling among terrestrial (atmospheric) and oceanic systems at the mid–GS-1
transition on the European continent. This second phase of GS-1 calls for a revision of
the well established model of dry and cold stadials during the last glacial period. |
|
|
|
|
|
|