Orbital, ice-sheet, and possible solar forcing of Holocene lake-level fluctuations in west-central Europe: A comment on Bleicher

Abstract

Bleicher (2013) discussed interpretations proposed by Magny (2004) that Holocene lake-level fluctuations in west-central Europe suggest possible solar forcing of climate. He pointed out that the method used by Magny (2004) is a variant of a cumulative probability function (CPF) and cannot prove solar forcing of central European lake-level changes. He concluded that only few episodes of lake-level changes are climatically driven and that non-climatic factors were dominating. While Bleicher’s paper offers a stimulating contribution to the general debate on CPFs, the present comment is based on an approach which, in contrast to CPFs, excludes any consideration of variations in the probabilities over the time intervals given by calibration of 14C dates, as well as any distinction between types of dates (radiocarbon versus tree ring). It produces a revised pattern of the mid-European high lake-level events for the whole Holocene, supporting the hypothesis proposed in Magny (2004). Comparisons with other regional and North Atlantic palaeoclimatic records suggest that, without excluding other forcing factors, the successive high lake-level events recognised in west-central Europe reflect a combination of three main forcing factors acting on millennial and centennial scales, i.e. orbitally driven changes in insolation, impacts of deglacial outbursts and, possibly, variations in solar activity. Finally, it is clear that further investigations are still needed in order to improve the chronological data set for mid-European lake-level fluctuations, with particular attention to better defining the beginning and end of events.

Late Holocene vegetation changes in relation with climate fluctuations and human activity in Languedoc (southern France)

“…They are also concurrent with the rapid vegetation and marine environment changes recorded in Mediterranean (e.g., Cacho et al, 2001;Fletcher et al, 2007;Frigola et al, 2007; e.g., Kotthoff et al, 2008;Schmiedl et al, 2010;Combourieu-Nebout et al, 2009Desprat et al, 2013;Fletcher and Zielhofer, 2013). These climatic events fit with the general picture of climate change depicted by lake-level fluctuations in central Europe and the northern Mediterranean (Magny, 2013;Magny et al, 2013). Moreover, they are contemporaneous with North Atlantic Bond events around 4200, 2800 and 1400 cal BP, underlining the efficient climatic coupling between the North Atlantic and the Mediterranean during the late Holocene (Fig.…”

“…Various Holocene climate archives are available from the Mediterranean and the Atlantic, such as marine ice-rafted debris in the North Atlantic (Bond et al, 2001), lake-level fluctuations in the Alps and the Mediterranean (Magny et al, 2002Magny, 2004Magny, , 2013, glacier oscillations in the Apennines (Giraudi, 2004(Giraudi, , 2005Giraudi et al, 2011), lake isotope records from the whole Mediterranean basin (Roberts et al, 2008) and changes in storminess (Sorrel et al, 2009;Sabatier et al, 2012). They highlight important climatic variations during the latter half of the Holocene which are correlated with vegetation changes.…”

Subfossil peatland trees as proxies for Holocene palaeohydrology and palaeoclimate

“…Netherlands are confirmed by other proxy records, which suggest rising lake levels (Magny, 2004(Magny, , 2013 There is still a need for improved understanding of the relations between peatland tree growth, 717 moisture variability, and climate dynamics, to enable more robust hydrology and climate 718 interpretation from peatland tree-ring, replication, and mean-age records. For example, there is a 719 clear need for new methods to isolate the temperature and precipitation signals in tree-growth 720 patterns.…”

Deglacial and Holocene vegetation and climatic changes in the southern Central Mediterranean from a direct land–sea correlation

“…5-11 ka, 10.3-9.9 ka, 9.5-9.1 ka, 8.5-7.9 ka, 7.3-6.7 ka, 6.4-6 ka, ∼ 5.5 ka and 4.5 ka. During the early Holocene dry phase, two centennial-scale dry and cold events at ∼ 11.2 ka and 10.1 ka are clearly marked by increases of semi-desert plants with lower tree (Fletcher and Sánchez Goñi, 2008): 3-points moving average (bold green line) with forest reduction episodes indicated by the grey bars as in Fletcher et al (2012); MD04-2797CQ pollen percentages and alkenone-SSTs (bold lines: cubic smoothing splines with a degree of freedom adjusted to highlight the centennial-scale changes) with abrupt vegetation and SST changes as described in the text; red and black symbols denote radiocarbon age control of core MD04-2797CQ; Mid-European lake level (LL) changes with high lake level phases as indicated in Magny (2013); Stacked Hematite Stained Grains (% HSG) from North Atlantic records (Bond et al, 2001). and shrubs percentages.…”