Neoglaciation in the Spanish Pyrenees: a multiproxy challenge

Abstract

Following the Holocene Thermal Maximum, dated between 11 and 6 ka, the Neoglacial period was one of the progressive, fluctuating cooling that peaked during the Little Ice Age (LIA). The almost total absence of glacial tills prior to the LIA in the Pyrenees forces recourse to a high variety of proxies, including lacustrine sediments, palynological records, dendroclimatology, ice cores from glaciers and caves, speleothems, historical documentation and glacial records. This has enabled us to identify several colder periods during the mid-and late-Holocene: (i) the first phase of the Neoglacial period occurred at some time around 6 ka; (ii) a glacial pulse immediately before 3.4 ka; (iii) a glacial re-advance during the Dark Ages, i.e., immediately before the Medieval Climate Anomaly, between the fourth and ninth centuries; and (iv) the Little Ice Age, which started at the beginning of the fourteenth century and finished in the mid-nineteenth century. During the LIA, there was remarkable climate variability, with two, and probably three, glacial pulses, mainly between 1620 and 1715 and in the first half of the nineteenth century. Of all of the Holocene cold periods, most of the European paleoclimatic records coincide on the occurrence of the LIA. For the remaining Holocene cold periods, European records show high variability and uncertainty, particularly for the onset of the Neoglacial, although the phases of glacial pulses in the Pyrenees broadly coincide with those identified in the Alps and northern Europe.

The case of a southern European glacier disappearing under recent warming that survived Roman and Medieval warm periods

“…the LIA, as inferred from three polished surfaces dated at 3500 ± 400, 2500 ± 300 and ± 100 Cl yr BP, indicating the occurrence of different deglaciation phases, and therefore glacial re-advances prior to these dates (García-Ruiz et al, 2020). Most likely, the voluminous moraine at the foot of the Monte Perdido Massif, which undoubtedly was deposited during the LIA, incorporates minor moraines and till from prior Neoglacial advances, as has been reported in other Pyrenean cirques (Crest et al, 2017;Palacios et al, 2017).…”

“…According to the age-depth model, the MPG experienced a spectacular retreat (Fig. 4D), including the complete melting of some minor glaciers in the Marboré Cirque (García-Ruiz et al, 2020). Nevertheless, during the MCA part of MPG was preserved, as we find ice from 0 to 700 CE.…”

“…4B). This situation probably continued during the following cold period, the Dark Ages (DA, Fig 4C) when the glacier advanced as indicated by the polished surface dated at 1100 ± 100 36 Cl yr BP (García-Ruiz et al, 2020). In glaciers in the Alps, reconstructions based on dating trees found within and at the edge of glacier forefields have revealed a minimum glacier extent during the Iron Age and the RP (Holzhauser et al, 2005), when glaciers were estimated to be smaller than during the 1920s (Ivy-Ochs et al, 2009).…”

“…Like other glaciers all over the world (Davis et al, 2009;Solomina et al, 2015), MPG likely experienced numerous spatial fluctuations during the Holocene, although absolute dates directly obtained from moraines are uncertain. A single boulder was dated from the outermost moraine corresponding to the maximum glacier expansion since the Younger Dryas (recalculated at 6900 ± 800 36 Cl yr BP) (García-Ruiz et al, 2020) in the Marboré Cirque. This is the oldest Holocene date available for glacial deposits in Spain (García-Ruiz et al, 2014), and indicates a glacier advance during the Neoglacial period (Fig.…”

The case of a southern European glacier which survived Roman and medieval warm periods but is disappearing under recent warming

“…Vertical cores were not recovered because the glacier does not meet the usual glacio-meteorological and topographical criteria required to obtain a preserved ice core stratigraphy. The unfulfilled criteria include low temperatures to prevent water percolation and a large extension and flat surface topography to minimise the influence of glacier flow (Garzonio et al, 2018). Samples were collected in an area with no evidence of major current ice movement, as confirmed by results from interferometric radar and global navigation satellite system (GNSS) measurements (López- Moreno et al, 2019).…”