Paleoclimate in continental northwestern Europe during the Eemian and early Weichselian (125–97 ka): insights from a Belgian speleothem

Abstract

Abstract. The last interglacial serves as an excellent time interval for studying climate dynamics during past warm periods. Speleothems have been successfully used for reconstructing the paleoclimate of last interglacial continental Europe. However, all previously investigated speleothems are restricted to southern Europe or the Alps, leaving large parts of northwestern Europe undocumented. To better understand regional climate changes over the past, a larger spatial coverage of European last interglacial continental records is essential, and speleothems, because of their ability to obtain excellent chronologies, can provide a major contribution. Here, we present new, high-resolution data from a stalagmite (Han-9) obtained from the Han-sur-Lesse Cave in Belgium. Han-9 formed between 125.3 and ∼ 97 ka, with interruptions of growth occurring at 117.3-112.9 and 106.6-103.6 ka. The speleothem was investigated for its growth, morphology and stable isotope (δ 13 C and δ 18 O) composition. The speleothem started growing relatively late within the last interglacial, at 125.3 ka, as other European continental archives suggest that Eemian optimum conditions were already present during that time. It appears that the initiation of Han-9 growth is caused by an increase in moisture availability, linked to wetter conditions around 125.3 ka. The δ 13 C and δ 18 O proxies indicate a period of relatively stable conditions after 125.3 ka; however, at 120 ka the speleothem δ 18 O registered the first signs of regionally changing climate conditions, being a modification of ocean source δ 18 O linked to an increase in ice volume towards the Marine Isotope Stage (MIS) 5e-5d transition. At 117.5 ka, drastic vegetation changes are recorded by Han-9 δ 13 C immediately followed by a cessation of speleothem growth at 117.3 ka, suggesting a transition to significantly dryer conditions. The Han-9 record covering the early Weichselian displays larger amplitudes in both isotope proxies and changes in stalagmite morphology, evidencing increased variability compared to the Eemian. Stadials that appear to be analogous to those in Greenland are recognized in Han-9, and the chronology is consistent with other European (speleothem) records. Greenland Stadial 25 is reflected as a cold/dry period within Han-9 stable isotope proxies, and the second interruption in speleothem growth occurs simultaneously with Greenland Stadial 24.

Stable isotope compositions of speleothems from the last interglacial – Spatial patterns of climate fluctuations in Europe

“…It is interesting to note that the BAR-II δ 18 O carb record indicates a strongly arid pulse in the same period that points again to the decisive connection between the Mediterranean moisture availability and the Carpathian Regions's hydroclimate. The period of elevated δ 18 O values ends with a decrease at about 117 ka that occurred contemporaneously with the growth stop of the Han-sur-Lesse stalagmite (Vansteenberge et al, 2016) and the steep δ 18 O decrease in the TKS record (Meyer et al, 2008), suggesting different responses in the regional temperature and humidity changes in Western and Central Europe to the largescale event triggering the GS26 cooling at Greenland.…”

“…Fewer than a dozen speleothem C and O isotope records represent at least a part of the LIG in Europe (Linge et al, 2001;Holzkämper et al, 2004;Drysdale et al, 2005;Muñoz-García et al, 2007;Meyer et al, 2008;Couchoud et al 2009;Boch et al, 2011;Genty et al, 2013;Regattieri et al, 2014;Moseley et al, 2015), and only a few of them cover more than 10 ka including peak interglacial conditions as well as the glacial inception (Drysdale et al, 2005;Meyer et al, 2008;Drysdale et al, 2009;Moseley et al, 2015;Vansteenberge et al, 2016). In this section the BAR-II data will be compared with eleven stalagmite records from Europe and the Levant (Fig.…”

“…The Hansur-Lesse stalagmite is characterized by a δ 18 O carb rise of ~0.6‰ at about 120 ka, which was related to a shift in the moisture source due to the starting growth of polar ice sheets (Vansteenberge et al, 2016). The Entrische cave's TKS record (Meyer et al, 2008) (Boch et al, 2011;Moseley et al, 2015).…”

“…As discussed above, low δ 13 C values indicate increased humidity, and the same (with relative increase of winter precipitation) is assumed for the low δD values (see above). Regional humidity proxies are provided for the period by the carbon isotope compositions of the Han-9 stalagmite (Hansur-Lesse Cave, Vansteenberge et al, 2016) and the BDinf stalagmite (Bourgeois-Delaunay Cave, Couchoud et al, 2009) that can serve as independent test records. Fig.…”

“…Compared to earlier periods, stalagmites from the last interglacial (LIG) are rather frequent and can be studied in sufficient numbers (Govin et al, 2015). Stable C and O isotope records, for instance, from European caves' carbonate deposits are available from Belgium (Vansteenberge et al, 2016), the Alps (Austria; Meyer et al 2008, Boch et al, 2011Moseley et al 2015), the Massif Central (France; Couchoud et al 2009), and the Apuane Alps (Italy; Drysdale et al, 2005;2007). These records have been dated by the U-Th series dating method providing numerical ages, making them valuable for paleoclimate studies on the LIG, although their geochemical compositions have not been evaluated in detail as yet (Govin et al, 2015).…”