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Little Ice Age


      THE LITTLE ICE AGE



The Little Ice Age was a period of cooling that occurred after a warmer era known as the Medieval Warm Period.  It is conventionally defined as a period extending from the 16th to the 19th centuries.  It is generally agreed that there were three minima, beginning about 1650, about 1770, and 1850, each separated by intervals of slight warming. 

 

Starting in the 13th century, pack ice began advancing southwards in the North Atlantic, as did glaciers in Greenland.  The three years of torrential rains beginning in 1315 ushered in an era of unpredictable weather in North Europe which did not lift until the 19th century.  There is anecdotal evidence of expanding glaciers almost worldwide.  In contract, a climate reconstruction based on glacial length shows no great variation from 1600 to 1850 , though it shows strong retreat thereafter. 

 

For this reason, any of several dates ranging over 400 years may indicate the beginning of the Little Ice Age (while not a true ice age):

 

·         1250 for when Atlantic pack ice began to grow

·         1300 for when warm summers stopped being dependable in Northern Europe

·         1315 for the rains and Great Famine of 1315-1317

·         1550 for theorized beginning of worldwide glacial expansion

·         1650 for the first climatic minimum.

 

In contrast to its uncertain beginning, there is a consensus that the Little Ice Age ended in the mid-19th century.  

 

 

                       

 

 

Northern Hemisphere (America)

 

The Little Ice Age brought colder winters to parts of Europe and North America.  Canals and rivers in Great Britain and the Netherlands were frequently frozen deeply enough to support ice skating and festivals.  The first River Thames frost fair was in 1607; the last in 1814, although changes to the bridges and the addition of an embankment affected the river flow and depth, hence diminishing the possibility of freezes.  The Baltic Sea froze over, enabling sledge rides from Poland to Sweden, with seasonal inns built on the way.  The winter of 1794-1795 was particularly harsh when the French invasion army under Pichegru could march on the frozen rivers of the Netherlands, while the Dutch fleet was fixed in the ice in Den Helder harbor.  In the winter of 1780, New York Harbor froze, allowing people to walk from Manhattan to Staten Island.  Sea ice surrounding Iceland extended for miles in every direction, closing that island’s harbors to shipping. 

 

The severe winters affected human life in ways large and small.  The population of Iceland fell by half, but this was perhaps also due to fluorosis caused by the eruption of the volcano Laki in 1783.  Iceland also suffered failures of cereal crops and people moved away from a grain-based diet.  The Norse colonies in Greenland starved and vanished (by the 15th century) as crops failed and livestock could not be maintained through increasingly harsh winter.  In North America, American Indians formed leagues in response to food shortages.  In Southern Europe, in Portugal, snow storms were much more frequent while today they are rare.  There are reports of heavy snowfalls in the winters of 1665, 1744 and 1886.

 

Crop practices throughout Europe had to be altered to adapt to the shortened, less reliable growing season, and there were many years of death and famine (such as the Great famine if 1315-1317, although this may have been before the LIA proper).  Violent storms cause massive flooding and loss of life.  Some of these resulted in permanent losses of large tracts of land from the Danish, German, and Dutch coasts.

 

In Ethiopia and Mauritania, permanent snow was reported on mountain peaks at levels where it does not occur today.  Timbuktu, an important city on the trans-Saharan caravan route, was flooded at least 13 times by the Niger River; there are no records of similar flooding before or since.  In China, warm weather crops, such as oranges, were abandoned in Jiangxi Province, where they had been grown for centuries.  In North America, settlers also reported severe winters.  For example, in 1607-1608 ice persisted on Lake Superior until June.  The journal of Pierre de Troyes Chevalier de Troyes, who led an expedition to James Bay in 1686, recorded that James Bay was still littered with so much floating ice that he could hide behind it in his canoe on July 1. 

 

In the late 17th century, agriculture had dropped off so dramatically that "Alpine villagers lived on bread made from ground nutshells mixed with barley and oat flour.  "Finland lost perhaps a third of its population to starvation and disease. 

 

Scottish painting and contemporary records demonstrate that curling and skating were formerly popular outdoor winter sports, but it is now seldom possible to curl outdoors in Scotland due to unreliable conditions.

 

 

Southern Hemisphere     

 

Since the discovery of the Little Ice Age, there have been doubts about whether it was a global phenomenon or a cold spell restricted to the Northern Hemisphere.  In recent years, several scientific works have pointed out the existence of cold spells and climate changes in areas of the Southern Hemisphere, and their correlation to the Little Ice Age. 

 

 

Africa

 

In Southern Africa, sediment cores retrieved from Lake Malawi show colder conditions between 1570 and 1820, suggesting the lake Malawi records "further support, and extend, the global expanse of the Little Ice Age”. 

 

A novel 3000 year temperature reconstruction method based on the rate of stalagmite growth in a cold cave in South Africa suggest a cold period from 1500 to 1800 "characterizing the south African Little Ice age”. 

 

 

Antarctica

 

Kreutz et al. (1997) compared results from studies of West Antarctic ice cores with the Greenland Ice Sheet Project Two (GISP2) and suggested a synchronous global Little Ice Age (LIA). 

 

The Siple Dome (SD) has a climate event with an onset time that is coincident with that of the LIA in the North Atlantic based on a correlation with the GISP2 record.  This event is the most dramatic climate event seen in the SD Holocene glaciochemical record.  The Siple Dome ice core also contained its highest rate of melt layers (up to 8%) between 1550 and 1700, most likely due to warm summers during the LIA. 

 

Law Dome ice cores show lower levels of CO2 mixing ratios during 1550 to 1800 AD, leading investigators Etheridge and Steele to conjecture "probably as a result of colder global climate”. 

 

 

Australia, New Zealand and Pacific Islands   

 

There is limited evidence about condition in Australia, though lake records in Victoria suggest that conditions, at least in the south of the state, were wet and/or unusually cool.  In the north of the continent the limited evidence suggests fairly dry conditions, while coral cores from the Great Barrier Reef show similar rainfall today but with less variability.  A study that analyzed isotopes in Great Barrier Reef corals suggested that increased water vapor transport from southern tropical oceans to the poles contributed to the LIA.

 

Paleosea-level data for the Pacific Islands suggest that sea level in the region fell, possibly in two stages, between AD 1270 to 1475.  This was associated with a 1.5ºC fall in temperature (determined from oxygen isotope analysis) and an observed increase in EL Niño frequency. 

 

In the Southern Alps of New Zealand, the Franz Josef glacier advanced rapidly during the Little Ice Age, reaching its maximum extent in the early 18th century, in one of the few places where a glacier thrust into rain forest. 

 

 

South America   

 

Tree ring data from Patagonia show cold episodes between 1270 and 1380, and from 1520 to 1670;  periods contemporary with LIA events in the Northern Hemisphere.  Eight sediment cores taken from Puyehue Lake have been interpreted as showing a humid period from 1470 to 1700, which the authors describe as a regional marker of LIA onset.  

 

Although it only provides anecdotal (based on or consisting of reports or observations of usually unscientific observers) evidence, in 1675 the Spanish explorer Antonio de Vea entered San Rafael Lagoon through Rio Tempanos (Spanish for Ice Floe River), without mentioning any ice floe, and stated that the San Rafael Glacier did not reach far into the lagoon.  In 1766 another expedition noticed that the glacier did reach the lagoon and calved into large icebergs.  Hans Steffen visited the area in 1898, noticing that the glacier penetrated far into the lagoon.  "the recognition of the LIA in Northern Patagonia, through the use of documentary sources, provides important, independent evidence for the occurrence of this phenomenon in the region”.  As of 2001, the border of the glacier has significantly retreated compared to the borders of 1675.

 

 

Climate Patterns 

 

In the North Atlantic, sediments accumulated since the end of the last ice age, nearly 12,000 years ago, show regular increases in the amount of coarse sediment grains deposited from icebergs melting in the now open ocean, indicating a series of 1 to 2ºC (2 to 4ºF) cooling events recurring every 1,500 years or so (Bond et al., 1997).  The most recent of these cooling events was the Little Ice Age.  These same cooling events are detected in sediments accumulation off Africa, but the cooling events appear to be larger, ranging between 3 to 8ºC (6 to 14ºF).

 

 

Causes

 

Scientists have tentatively identified these causes of the Little Ice Age as decreased solar activity, increased volcanic activity, altered ocean current flows, the inherent variability of global climate, and reforestation following decreases in the human population.    

 

Please refer to "MECHANISMS” in the site menu under Ice Ages.

 

 

End of the Little Ice Age

 

Beginning around 1850, the climate began warming and the Little Ice Age ended.

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