Glacial Advance During The Little Ice Age

By Paul Homewood

 

From HH Lamb’s “Climate, History and the Modern World”

 

We know that sea levels have risen since the late 19thC, and that much of this is due to melting of glaciers and ice sheets. However, we also know that the same glaciers were growing rapidly during the Little Ice Age, so can we say that 20thC sea level rise is anything other than a natural process?

 

Let’s remind ourselves of just how great and widespread this glacial advance was.

 

The history of glacial advance in the European Alps is well documented. Historian, Brian Fagan, offers us this horrifying account:

 

 

In the 16th Century the occasional traveller would remark on the poverty and suffering of those who lived on the marginal lands in the glacier’s shadow. At that time Chamonix was an obscure poverty stricken parish in “a poor country of barren mountains never free of glaciers and frosts…half the year there is no sun…the corn is gathered in the snow…and is so mouldy it has to be heated in the oven”. Even animals were said to refuse bread made from Chamonix wheat. Avalanches caused by low temperatures and deep snowfall were a constant hazard. In 1575 a visitor described the village as “a place covered with glaciers…often the fields are entirely swept away and the wheat blown into the woods and onto the glaciers”.

In 1589 the Allalin glacier in Switzerland descended so low that it blocked the Saas valley, forming a lake. The moraine broke a few months later, sending floods downstream. Seven years later 70 people died when similar floods from the Gietroz glacier submerged the town of Martigny.

As the glaciers relentlessly pushed downslope thousands of acres of farm land were ruined and many villages were left uninhabitable such as La Bois where a government official noted “where there are still six houses. all uninhabited save two, in which live some wretched women and children…Above and adjoining the village there is a great and horrible glacier of great and incalculable volume which can promise nothing but the destruction of the houses and lands which still remain”. Eventually the village was completely abandoned.

The same official visited the hamlet of La Rosiere in 1616 and found" “The great glacier of La Rosiere every now and then goes bounding and thrashing or descending…There have been destroyed 43 journaux of land with nothing but stones and 8 houses, 7 barns and 5 little granges have been entirely ruined and destroyed”.

Alpine glaciers, which had already advanced steadily between 1546 and 1590, moved aggressively forward again between 1600 and 1616. Villages that had flourished since medieval times were in danger or already destroyed. During the long period of glacial retreat and relative quiet in earlier times, opportunistic farmers had cleared land within a kilometer of what seemed to them to be stationary ice sheets. Now their descendants paid the price with their villages and livelihoods threatened.

Between 1627 and 1633 Chamonix lost a third if its land through avalanches, snow, glaciers and flooding, and the remaining hectares were under constant threat. In 1642 the Des Bois glacier advanced “over a musket shot every day, even in August”.

By this time people near the ice front were planting only oats and a little barley in fields that were under snow for most of the year. Their forefathers had paid their tithes in wheat. Now they obtained but one harvest in three and even the grain rotted after harvesting. “The people here are so badly fed they are dark and wretched and seem only half alive”.

In 1715 the village of Le Pre-du-Bar vanished under a glacier caused landslide. The glacial high tide in the Alps came around 1750 and gradually the glaciers began their retreat, much to the relief of the people who lived there.

 

HH Lamb, in “Climate: Past, Present & Future”, puts these glacial advances into perspective:

And at their subsequent advanced positions – probably around 500 BC as well as between 1650 and 1850 AD – the glaciers in the Alps regained an extent, estimated in the Glockner region, at about 5 times their Bronze Age Minimum, when all the smaller ones had disappeared.

 

But the Little Ice Age was not only restricted to Europe. A scientific study by Ingolfsson et al found that Icelandic glaciers reached their Holocene maximum during this period:

Iceland was heavily glaciated at the Last Glacial Maximum – glaciers extended towards the shelf break. Ice thickness reached 1,500±500 m. The rapid deglaciation, starting 17.5–15.4 cal. kyr BP, was controlled by rising global sea level. The marine part of the ice sheet collapsed 15.4–14.6 cal. kyr BP and glaciers retreated inside the present coastline. In Younger Dryas, 12.6–12.0 cal. kyr BP, the ice sheet readvanced and terminated near the present coastline. After 11.2 cal. kyr BP the ice sheet retreated rapidly and relative sea level fell towards and eventually below present sea level at 10.7 cal. kyr BP. At 8.7 cal. kyr BP glaciers terminated proximal to their present margins. During the mid-Holocene climate optimum some of the present-day ice caps were probably absent. Ice caps expanded after 6.0–5.0 cal. kyr BP, and most glaciers reached their Holocene maxima during the Little Ice Age (AD 1300–1900).

 

Across in Greenland, not only do we have the history of Viking colonies during the Middle Ages, we also have ice core data showing that temperatures in Greenland were about 1.5 C warmer 1000 years ago than now, but also that the period around 1875, at the lowest point of the Little Ice Age, marked the coldest point in the last 10,000 years.

Meanwhile, analysis of moraines shows that the Greenland Ice Sheet may have receded tens of kilometers within its present day margins during the early and mid Holocene, before reaching their maximum extents since the early Holocene during the Little Ice Age.

 

Over in Alaska, it has been found that there were three separate glacial advances between the 12thC and 18thC. Remains of trees, dating back to the Middle Ages, are now reappearing there as the glaciers retreat.

 

Brian Fagan also describes how:

Ice sheets in Alaska, the Canadian Rockies and Mount Rainier in the NW United States moved forward simultaneously. Glaciers expanded at the same times during the 19th Century in the Caucasus, the Himalayas and China.

The Qualccaya ice core in Peru provides evidence of frequent intense cold from 1500 to 1720, with prolonged droughts and cold cycles from 1720 to 1860.

 

Studies of glaciers in South America come to similar conclusions.

Thompson on the Quelccaya glacier in Peru:

The fact that the Little Ice Age (about A.D. 1500 to 1900) stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event.

Areneda, on the Cipreses Glacier in Chile:

These data allow us to infer that the last maximum advance of Cipreses glacier, in Chile, attributable to the ‘Little Ice Age’ occurred around AD 1842. The first historical retreat was recorded in 1858 and, since then, the glacier has shown a clear retreating trend with no new advances.

And Areneda again, this time on the San Rafael glacier in Chile:

Past ice lobe behaviour at Laguna San Rafael is described in documents provided by Spanish and then Chilean explorers from the late seventeenth to the early twentieth centuries. These records begin in AD 1675, when temperate conditions, probably similar to those at present, prevailed. At that point, the glacier was confined within its valley, not penetrating the Laguna. The glacier advanced noticeably during the nineteenth century and probably reached a maximum position for the `Little Ice Age’ around AD 1875

 

Finally, even glaciers in New Zealand underwent massive expansion, as Brian Fagan relates:

In New Zealand the Franz Joseph glacier was “a mere pocket of ice on a frozen snowfield nine centuries ago”…. Then Little Ice Age cooling began and the glacier thrust downslope into the valley below smashing into the great rain forests that flourished there, felling giant trees like matchsticks. By the early 18th Century, Franz Joseph’s face was within 3 km of the Pacific Ocean .

The high tide of glacial advance at Franz Joseph came between the late 17th Century and early 19th Century, just as it did in the European Alps.

 

 

 

It is evident that sea levels must have fallen during the Little Ice Age, not only because of glacial advance but also because of colder temperatures. Were sea levels higher than now during the MWP? Certainly HH Lamb believes so – see here.

But even if they were not, it is clear that much of the 20thC rise in sea levels that we have seen is no more than a return to the conditions that existed 1000 years ago, before glaciers worldwide began to expand.

We do know that much of the glacial retreat since the 19thC actually took place before the middle of the 20thC, as the photo at the top illustrates.

 

There is no written law of nature that says glaciers should be the size they were in Victorian times. Indeed, there is no reason why they should not return to their state 4000 years ago.

As HH Lamb writes in “Climate, History and The Modern World” (pp 146).

“Most – and perhaps all – of the glaciers present today in the United States Rockies south of the Canadian border are believed to have formed since 1500 BC.”