Alps were Ice-Free around 3,350 Years Ago, According to the Peer-Reviewed Literature Published in 'Nature'

Following 'the Science™' Reveals More Evidence of Us Living in Comparatively Cold Times, Which Has, Arguably, Major Implications for Public Policy Aims Related to Climate Change™

This is a follow-up posting to me bringing up a recent article about Norwegian glaciers—or the lack thereof—as recent as 1,500 years ago:

Today, I wish to draw your attention to yet another piece of comparable evidence, which appeared in Nature. Entitled, ‘New glacier evidence for ice-free summits during the life of the Tyrolean Iceman’, the paper by Bohleber et al. appeared in Scientific Reports volume 10, Article number: 20513 (2020). Source. It’s ‘OpenAccess’, hence, please go ahead and check it out.

On this Sunday, I wish to take you back to the days of the ‘Tyrolean Iceman’, or Ötzi:

Ill.: Reconstruction of Ötzi mummy as shown in Prehistory Museum of Quinson, Alpes-de-Haute-Provence, France (via Wikipedia).

Ice-Free Summits in the Alps c. 3,350 Years Ago

From the paper by Bohleber et al. (references omitted, emphases added):

Abstract

Detailed knowledge of Holocene climate and glaciers dynamics is essential for sustainable development in warming mountain regions. Yet information about Holocene glacier coverage in the Alps before the Little Ice Age stems mostly from studying advances of glacier tongues at lower elevations. Here we present a new approach to reconstructing past glacier low stands and ice-free conditions by assessing and dating the oldest ice preserved at high elevations. A previously unexplored ice dome at Weißseespitze summit (3500 m), near where the ‘Tyrolean Iceman’ was found, offers almost ideal conditions for preserving the original ice formed at the site. The glaciological settings and state-of-the-art micro-radiocarbon age constraints indicate that the summit has been glaciated for about 5900 years. In combination with known maximum ages of other high Alpine glaciers, we present evidence for an elevation gradient of neoglaciation onset. It reveals that in the Alps only the highest elevation sites remained ice-covered throughout the Holocene. Just before the life of the Iceman, high Alpine summits were emerging from nearly ice-free conditions, during the start of a Mid-Holocene neoglaciation. We demonstrate that, under specific circumstances, the old ice at the base of high Alpine glaciers is a sensitive archive of glacier change. However, under current melt rates the archive at Weißseespitze and at similar locations will be lost within the next two decades.

So far, glaciers have been studied mainly at lower elevation levels, indicating the staggeringly absurd presupposition that glaciers at higher elevations were, well, ‘always there’.

What Bohleber et al. are telling us here, though, is this: with its peak at approx. 3,500m above sea level, the Weißseespitze is a very high mountain that ‘has been glaciated for about 5900 years’. In other words, since it’s 2023, we shall subtract these from the number cited (5,900) and arrive at the conclusion that snow and ice packs on mountains as high as 3,500m above sea level is both a comparatively recent and an esp. unreliable indicator of the shape of things to come.

More from the paper:

Introduction

A major scientific question is whether this process of deglaciation is unprecedented within the Holocene…We already have comprehensive information about the maximum extent of Alpine glaciers from the investigation of moraine positions and ages. Yet comparatively little is known so far about the times of minimum ice cover or ice-free conditions at high-elevation…

Despite the strong retreat since the Little Ice Age (LIA), access to the oldest ice near bedrock is still complicated for high-elevation areas and usually requires drilling glacier ice cores.

Most previous ice core research in the Alps was aimed at continuous stratigraphic climate records. This limited it to glaciers where there is usually no melting on the surface throughout the year. Few suitable drilling sites exist as they are mostly confined to above 4000 m altitude, e.g. locations in the Western Alps. In the Eastern Alps and at elevations below 4000 m, such records are sparse, with only one ice core record obtained from an already partially temperate site at Ortler and at the temperate Silvretta glacier…

Until recently, only human artifact findings were discussed in connection with low stands of high-elevation glaciers in the Alps; at Schnidejoch pass (2750 m, Bernese Alps) and the ‘Tyrolean Iceman’ in the Eastern Alps…Radiocarbon dating of artifacts indicates three phases of minimal ice extent, suitable for crossing the pass. The earliest phase was around 6.8–6.3 ka cal [calibrated kiloanni before 1950, i.e., 4777-4,277 BCE], a second phase from 5.7 to 4.9 ka cal [3677-2877 BCE], and an adjacent third period from 4.9 to 4.2 ka cal [2877-2177 BCE]. The Tyrolean Iceman mummy emerged from a small ice field, vanished since, at Tisenjoch, a saddle located at 3210 m. Radiocarbon dating of the mummy indicated that the Iceman lived roughly 5.1–5.3 ka cal [3077-3277 BCE; don’t ask me why the authors inverted the dates here]. The well-preserved state of the corpse and of artifacts suggests that they had been conserved in frozen conditions. The ice field at Tisenjoch must therefore have been present during several known periods of glacier retreat, such as the Roman and Medieval warm phases…

Results

The Weißseespitze summit glacier (WSS, 3500 m) marks the highest point of Gepatschferner in the Austrian Alps. It is a unique site: (1) located only 12 km from the Iceman location, it offers a potential surrogate to investigate the local glacier conditions during the lifetime of the Iceman; (2) it has a dome-shaped glacier geometry, which is an extremely rare feature in the Alps… [see fig. 1, reproduced below]

Ice Core Analysis and Glacier Age Constraints

In March 2019, two parallel cores were drilled 11 m to bedrock at the ice divide with nearly flat bed conditions. Visible layers of refrozen meltwater indicate that there was only limited occasional melt at this site when this ice was formed. The main part of the ice core includes bubble-rich glacier ice, the likely result of dry metamorphosis of snow…

Discussion

…despite the drastic mass loss on the surface in today’s conditions, the basal ice was found to remain frozen to the bed. Our dating of the ice just above bedrock indicates that the ice body at WSS formed earlier than (5.9 ± 0.7) ka cal and has been glaciated continuously ever since. This implies that even the WSS summit location at 3500 m altitude was ice-free during an interval prior to (5.9 ± 0.7) ka [4577-3177 BCE]. In the context of other regional climate evidence, this finding is consistent with the glacier length reconstructions of Gepatschferner, which document a distinct minimal extent starting around 5.9 ka. Likewise, at around 5.3–5.1 ka cal [the era of the ‘Tyrolean Iceman’], no ice existed at nearby Tisenjoch, at 3210 m. The fact that the lifetime of the Iceman falls within the maximum age range determined for the WSS summit glacier suggests that a rather rapid neoglaciation ended the formerly near ice-free conditions at the summits in this region.

[more evidence] The end of the so-called ‘Holocene Climatic Optimum’ is also observed in Austrian stalagmite records, indicating the onset of a cooling period around 5.9 ka. In the Eastern Alps, tree-ring-dated subfossil wood remains indicate that several advances occurred between 5.9 and 5.5 ka at three different glaciers in the Alps: Unteraar, Pasterze, Tschierva. The former two have much longer response times than Tschierva, and generally fluctuations of glacier tongues deviate from mass balances at summit glaciers because the terminus position also depends on ice dynamics and because wind erosion affects net accumulation at summits. Nonetheless, the general picture agrees well. Around 5.9 ka [3877 BCE], there was a limited advance at Tschierva glacier, reaching the 2000 ice extent and ending the preceding warm period. During those warm periods, the tree line was up to 165 m above the 1980 tree line in Kaunertal, in ultimate vicinity to WSS. A chironomid record [i.e., fossilised or otherwise conserved flies] obtained at Schwarzsee in nearby Oetztal suggests that roughly between 5.2 and 4.5 ka cal a climate transition occurred, with a distinct cooling trend in summer temperatures, which prevailed until the end of the LIA [so the ‘Little Ice Age’ wasn’t that ‘little’ after all, for it began between 3177 and 2477 BCE and extended all the way until…around 1850].

This is consistent with other regional evidence provided by the Oberfernau bog sediments (Buntes Moor): a radiocarbon-dated layer marks the end of peat growth during a warm phase (Fig. 3). From about 4.2–3.9 ka cal onwards, the fluvioglacial sediments indicate the presence of glaciers in the catchment area, i.e. a cooler period. Although the effective altitude of the glaciers leading to the fluvioglacial deposits is not closely defined, it must have been significantly lower than the WSS summit. In this regional context, the findings from WSS fit remarkably well into a general picture of regional warm conditions ending around 5.9 ka at high altitude. This was followed by a period of glacier advance that started around the lifetime of the Iceman, with a delayed onset of glaciation on lower elevation summits…

The elevation-age gradient implies that in the Alps only the highest elevation sites, such as Colle Gnifetti, remained ice-covered throughout the Holocene. This view is corroborated by the fact that the summits above 4000 m show only minor volume changes even under current climate conditions. Regarding the presence of glaciers below 4000 m, Holocene climate variability has sufficed to induce their de- and subsequent neoglaciation…

Although the spatial density of dated ice archives is particularly high in the case of the Alps, our approach can, in principle, be transferred to other mountain ranges to study their Holocene neoglaciation history…it is worth noting that point mass balance data have been shown to reflect changes in climate better than total mass balance or terminus fluctuation. Cold high-elevation glaciers with low ice dynamics, as almost ideal–typical at WSS, thus present a more direct link to past climate change than terminus fluctuations…

Conclusions

In a compilation with existing glacier age constraints, the unique ice dome at Weißseespitze has closed a regional and altitudinal gap to reveal the first direct evidence for an elevation gradient of Holocene neoglaciation in the Alps. While only the highest elevation sites remained ice-covered throughout the Holocene, summits around 3000–4000 m were likely ice-free during the Mid-Holocene or covered by glaciers distinctly smaller than today. Around the lifetime of the Tyrolean Iceman and slightly earlier, rapid ice formation started and some of this ice cover exists to this day. Impressive current melt rates threaten the extinction of these ice archives: Weißseespitze glacier, which has accumulated over nearly 6000 years, may disappear within just two decades. However, it may not be the deglaciation of the summits during the Holocene that is unprecedented, but its pace, on which we urgently need extensive empirical information.

One aspect to consider here, methodologically-analytically speaking, is the alleged ‘unprecedented' pace of deglaciation. If we take the authors at their word, ‘rapid ice formation started around the lifetime of the Tyrolean Iceman’: how ‘rapid’ would that be, esp. in light of the ‘Little Ice Age’ ending around 1850, which indicates that the eventual (possible) disappearance of ice cover between 3000-4000m above sea level would occur over the course of some 200 years. Surely, this is ‘rapid’ or ‘very fast’ in geological terms—but would that be comparable in terms of its pace with the onset of glaciation between 3177 and 2477 BCE? Sadly, the authors provide no insights into these issues.

Bottom Lines

I find this fascinating: the more we learn about past climate change, the more we understand about our current moment.

Last month (see the article linked at the top), we learned that mountain passes around 1600m above sea level in Norway were ice-free some 1500 years ago.

This month, we learned that mountain peaks between 3000-4000m above sea level were ice-free as recent as ±6000 years ago.

Sure, there are differences in latitude to consider, but the picture that emerges is one that contradicts simplistic assumptions of current climate change, to say nothing about its future implications.

As regards the present moment, well, we can certainly state that ice-free mountain peaks some 6000 years ago were not related to human carbon dioxide emissions.

Thus follows that it becomes more and more epistemologically problematic to causally link ice-free mountain peaks between 3000-4000m—which also means higher altitudinal limits of tree growth—to human carbon dioxide emissions related to the burning of fossil fuels.

Mind you, I’m not claiming there’s no connection whatsoever, but the evidence before us becoming clearer and clearer: no single factor alone is able to explain anything (except, perhaps, for first-degree murder), and to quadruple down on 'decarbonising everything’ to ‘save the climate’ is becoming an ever-more problematic assumption.