Northern Iberian abrupt climate change dynamics during the last glacial cycle: A view from lacustrine sediments

Abstract

We present a palaeoclimatic reconstruction of the last glacial cycle in Iberia (ca. 120,000 -11,600 cal yrs BP) based on multiproxy reconstructions from lake sediments with robust chronologies, and with a particular focus on abrupt climate changes. The selected lake sequences provide an integrated approach from northern Iberia exploring temperature conditions, humidity variations and land-sea comparisons during the most relevant climate transitions of the last glacial period. Thus, we present evidence that demonstrates: i) cold but relatively humid conditions during the transition from MIS 5 to MIS 4, which prevailed until ca. 60,000 cal yrs BP in northern Iberia; ii) a general tendency towards greater aridity during MIS 4 and MIS 3 (ca 60,000 to 23,500 cal yrs BP) punctuated by abrupt climate changes related to Heinrich Events (HE), iii) a complex, highly variable climate during MIS 2 (23,500 to 14,600 cal yrs BP) with the "Mystery Interval" (MI: 18,500 to 14,600 cal yrs BP ) and not the global Last Glacial Maximum (LGM: 23,000 to 19,000 cal yrs BP) as the coldest and most arid period. The last glacial transition starts in synchrony with Greenland ice records at 14,600 cal yrs BP but the temperature increase was not so abrupt in the Iberian records and the highest humidity was attained during the Allerød (GI-1a to GI-1c) and not during the Bølling (GI-1e) period. The Younger Dryas event (GS-1) is discernible in northern Iberian lake records as a cold and dry interval, although Iberian vegetation records present a geographically variable signal for this interval, perhaps related to vegetation resilience.

What drives LGM precipitation over the western Mediterranean? A study focused on the Iberian Peninsula and northern Morocco

“…All these pollen assemblage zones agree with the evidence of LGM arid or semi-arid conditions. Isotopic δ 13 C analysis from the Banyoles site (ValeroGarcés et al 1998;Moreno et al 2012) also indicates a decrease of the primary productivity during the LGM, in agreement with drier conditions. Similarly, sedimentary and geochemical analyses carried out on the Estanya lake core reveal a predominance of saline waters at the LGM, a reduced organic productivity and a lake level about twice as low as today (Morellon et al 2009), also suggesting arid conditions, although the aridity was even more pronounced at the onset of the Holocene.…”

“…Increased moisture at the LGM, compared to the present-day period is supported by different observations such as the level of the Fuentillejo lake in central Spain (Vegas et al 2010 and review from Moreno et al 2012) and the river levels in northern Morocco (El Amrani et al 2008;Mercier et al 2009). However, these observations are in conflict with other records such as those obtained from continental pollen sequences (e.g.…”

“…Multi-proxy approaches (sedimentary facies, chemical and mineralogical analyses, geochemical composition, diatoms and pollen assemblages) applied to the four lacustrine records from the Fuentillejo lake (Central Spain, Vegas et al 2010), the Banyoles lake (ValeroGarcés et al 1998;Moreno et al 2012), the Estanya lake (Morellon et al 2009) and the La Salineta lake (ValeroGarcés et al 2004) bring information about past effective moisture content and/or about lake level variations (Minyuk et al 2007). Lake levels are not only affected by climatic parameters but also by inflows and outlets (unless the lake is considered to be a closed system) and by ice discharge from the surrounding melting glaciers.…”

A compilation of Western European terrestrial records 60–8 ka BP: towards an understanding of latitudinal climatic gradients

“…Finally, the 14 C method becomes increasingly imprecise and difficult to calibrate beyond 50,000 years . In such cases, other dating techniques are used, such as UeTh disintegration series on lacustrine carbonates (P erez-Obiol and Juli a, 1994), Optically Stimulated Luminescence (OSL) dating on siliciclastic sediments (Moreno et al, 2012) or palaeomagnetic excursions in particularly long records (Vegas et al, 2010). In addition to these absolute dating techniques, varve counting and tephras are widely used to provide a chronological framework (e.g.…”

“…South of the sub-and periglacial region, many sites provide records throughout large parts of MIS2 and 3 (Fletcher et al, 2010a;Moreno et al, 2012). Below, we discuss both regions of W Europe in more detail.…”