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Was The Franz Josef Glacier Smaller In The MWP?

March 18, 2013
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By Paul Homewood

 

 

The Franz Josef Glacier is one of New Zealand’s most iconic places. Situated in the Southern Alps, and named after the Austrian Emperor by a German explorer, it is one of the few glaciers in the world that extends down into a temperate rainforest.

Like most of the world’s glaciers, it has been in retreat since the Little Ice Age. But in Brian Fagan’s excellent book, “The Little Ice Age”, there is the following interesting reference to the Franz Josef :-

 

 

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“A Pocket Of Ice”

According to Fagan, the glacier must have been much smaller even than today in the MWP. But, unfortunately, he gives no reference to back up his statement, so I decided to do a bit of detective work! It immediately became apparent that very little work has been done on glacial fluctuations in New Zealand. Having contacted a couple of academic sources in NZ, I was put in touch with John Appleby, who had recently completed his PhD on Fox Glacier, ( a neighbour of the Franz Josef).

 

John kindly sent me his thesis, which, although mainly concerned with glacial processes, did have a small historical segment. This threw up two interesting facts:-

 

1) There is common acceptance that during the latter part of the Holocene Epoch (the last 11.5 kyr), a cooling of the global climate resulted in a growth of Polar and mountain glaciers (Clapperton, 1993, Porter, 2000, Renssen et al., 2007, Kelly et al., 2008). This ‘Neoglacial’ period of advance followed the hypsithermal or Holocene Climatic Optimum (occurring approximately 6-7 kyr BP (Iriondo, 1999)), and culminated between ~5.4 and 4.9 kyr BP (Porter, 2000), however, Thompson, et al. (2006) and Schaefer, et al. (2009) suggest Neoglaciation may have occurred as early as 6.4 kyr BP, dependent on location. Schaefer, et al. (2009) summarised Holocene glacial fluctuations in the Southern Alps (Figure 2.8) relative to fluctuations of glaciers in North America and Europe during the time period.

 

2) More recently, a detailed chronology of Little Ice Age (LIA) glacial advances has been detailed for Europe (Grove, 1988, Grove, 2001, Mann, 2002). Very little work exists on glacier fluctuations in New Zealand during this period, and those ages that do exist do not correspond directly with the European LIA models. Dates of LIA maximum cooling events in New Zealand, range from as early as AD1600 (Wardle, 1973, Gellatly, 1985, McKinzey et al., 2004) to the mid-1700s depending on the response time of certain glaciers (Chinn et al., 2005). The first surveys around the mid- to late-19th and early 20th Century (Figure 2.9) showed most glaciers in the region were still close to their LIA maximum positions (Gellatly, 1985, Chinn, 1996).

So this tells us that

  • The pattern of a Holocene Optimum followed by Neoglaciation, that we see time and again in the Northern Hemisphere, is also evident in NZ.
  • Glaciers reached a maximum during the LIA, and were still near that maximum in the early 20thC.

 

Finally, John’s paper shows the following table:-

 

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The key part to note is the plot of summer temperatures in NZ, based on tree ring reconstruction. Take a closer look.

 

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Temperatures were higher than now about 500 years ago, and also about 700-800 years ago.

 

The Encyclopaedia of New Zealand adds a bit more to the Holocene history:-

 

Since then [11000 BP] the glaciers of the Southern Alps have continued an irregular retreat. They reached their minimum size about 6,000 years ago, when the climate was warmer than now. There have been minor advances during cooler periods such as the ‘Little Ice Age’ from the 15th to the mid-19th century.

 

Before I move onto temperature reconstructions, there is one more piece of evidence, presented by Jean Grove, one of the 20thC’s top experts on glaciers and still regarded by glaciologists as “the first port of call”.

According to her, datable remains of tree stumps that emerged as the glacier retreated in the late 20thC have been carbon dated to the 6th and 7thC. Clearly the glacier was not bigger than today back then. Grove is clear on the significance of her researches worldwide:-

The first phase of the LIA began around the 13thC in all regions for which there is evidence. [i.e. globally]……The available evidence suggests that the MWP was global in extent.

Temperature Reconstructions

I have not managed to track down any other direct evidence regarding NZ glaciers, but there is a wealth of other evidence that suggests MWP temperatures in NZ were as high as, if not higher than, today.

According to Wikipedia,

A 1979 study from the University of Waikato found that "Temperatures derived from an 18O/16O profile through a stalagmite found in a New Zealand cave (40.67°S, 172.43°E) suggested the Medieval Warm Period to have occurred between AD 1050 and 1400 and to have been 0.75 °C warmer than the Current Warm Period." The MWP has also been evidenced in New Zealand by an 1100-year tree-ring record.

The  stalagmite studies are based on a paper by Wilson, Hendy and Reynolds, here, whilst the tree ring study is the one quoted by John Appleby above. The latter is from a paper by Cook, Palmer and D’Arrigo  here. Their abstract states:-

 

The occurrence of the Medieval Warm Period (MWP) in the Southern Hemisphere is uncertain because of the paucity of well-dated, high-resolution paleo-temperature records covering the past 1,000 years. We describe a new tree-ring reconstruction of Austral summer temperatures from the South Island of New Zealand, covering the past 1,100 years. This record is the longest yet produced for New Zealand and shows clear evidence for persistent above-average temperatures within the interval commonly assigned to the MWP. Comparisons with selected temperature proxies from the Northern and Southern Hemispheres confirm that the MWP was highly variable in time and space. Regardless, the New Zealand temperature reconstruction supports the global occurrence of the MWP.

There are other studies as well that confirm the MWP in NZ. According to Lorrey et al, another study of stalagmites shows,

for both the ENI and WSI δ18O records master speleothem histories, their warmest periods fall within the AD 900-1100 time interval.

Another speleotherm study in NZ by Williams et al came up with similar results, revealing,

a warmer-than-present "late-Holocene warm peak" between 0.9 and 0.6 ka BP that they equate with the Medieval Warm Period in Europe.  In New Zealand, they note that this period "coincided with a period of Polynesian settlement (McGlone and Wilmshurst, 1999)."  Thereafter, they report that temperatures "cooled rapidly to a trough about 325 years ago," which they say "was the culmination of the ‘Little Ice Age’ in Europe."

 

Conclusions

Piecing together the various strands of evidence, it is clear that the MWP in New Zealand was at least as warm as now, and probably warmer, and that the glaciers expanded rapidly to reach a maximum during the 18th and 19thC.

Although it cannot be directly quantified, it seems likely that Brian Fagan’s claim that the Franz Josef was just a “mere pocket of ice nine centuries ago” is a fair description.

And they did not even have SUV’s in those days.

One Comment
  1. Dr K.A. Rodgers permalink
    March 19, 2013 12:24 am

    Be very careful with the Encyclopedia of New Zealand. I was asked to write for it some ten years ago. I opted out when I found I was expected to adhere to a subjective environmentalist agenda by the editor concerned.

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