Publikationsdatum:
2018-03-06
Beschreibung:
CO2-induced global warming will affect seasonal to decadal temperature patterns. Expected changes will be particularly
strong in extratropical regions where temperatures will increase at faster rates than at lower latitudes.
Despite that, it is still poorly constrained how precisely short-term climate dynamics will change in a generally
warmer world, particularly in nearshore surface waters in the extratropics, i.e., the ecologically most productive
regions of the ocean on which many human societies depend. Specifically, a detailed knowledge of the relationship
between pCO2 and seasonal SST is crucial to understand interactions between the ocean and the atmosphere.
In the present investigation, we have studied for the first time how rising atmospheric pCO2 levels forced surface
temperature changes in Central Europe (paleolatitude ~45 °N) during the mid-Oligocene (fromca. 31 to 25Ma),
a time interval of Earth history during which global conditions were comparable to those predicted for the next
few centuries. For this purpose, we computed numerical climate models for the Oligocene (winter, summer,
annual average) assuming an atmospheric carbon dioxide rise from 400 to 560 ppm (current level to two
times pre-industrial levels, PAL) and from 400 to 840 ppm (= three times PAL), respectively. These models
were compared to seasonally resolved sea surface temperatures (SST) reconstructed from δ18O values of fossil
bivalve shells (Glycymeris planicostalis, G. obovata, Palliolum pictum, Arctica islandica and Isognomon maxillata
sandbergeri) and shark teeth (Carcharias cuspidata, C. acutissimaand Physogaleus latus) collected fromthe shallow
water deposits of the Mainz and Kassel Basins (Germany). Multi-taxon oxygen isotope-based reconstructions
suggest a gradual rise of temperatures in surface waters (upper 30 to 40m), on average, by asmuch as 4 °C during
the Rupelian stage followed by a 4 °C cooling during the Chattian stage. Seasonal temperature amplitudes increased
by ca. 2 °C during the warmest time interval of the Rupelian stage,withwarming beingmore pronounced
during summer (5 °C) than during winter (3 °C). According to numerical climate simulations, the warming of
surface waters during the early Oligocene required a CO2 increase by at least 160 ppm, i.e., 400 ppm to
560 ppm. Given that atmospheric carbon dioxide levels predicted for the near future will likely exceed this
value significantly, the Early Oligocene warming gives a hint of the possible future climate in Central Europe
under elevated CO2 levels.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Article
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