Medieval glaciation

Little Ice Age

End of the Little Ice Age

• 1860-80s: Evidence of pronounced glacier withdrawal all over continental Europe; many Alpine glaciers retreated >1 km by end of 19th century. Icelandic glaciers remained in advanced positions, however.

• 1870: Athabasca glacier of the Columbia Icefield (Alberta, Canada) advanced to near its Little Ice Age maximum completely blocking Sunwapta valley. Other glaciers in western Canada experienced major expansions.

• 1873: Beginning two decades of extreme winters in the northern Great Plains of the United States (Laskin 2004). During a January blizzard temperature reached -40 °C, and 70 people died in Minnesota. Another blizzard in March blew snow into fanatistic drifts up to 18 m tall. A third blizzard struck in April. Average wind speed exceeded 60 km/h for nearly 100 hours at Yankton, South Dakota.

• 1880 to present: Warm and wet climate in the Lvliang Mountains of north-central China (Liu et al. 2014).

• 1880-81: Known as the Snow Winter in the northern Great Plains of the United States (Laskin 2004). Blizzards began in October and continued into the next spring. Deep snow blocked railroads to Sioux Falls, South Dakota until mid-June. Widespread flooding took place in the Missouri River basin when snow finally melted in late spring.

• Late 1800s: Little Ice maximum in western Canada, which is contrary to general glacier retreat in most other part of the world.

  	View from crest of Little Ice Age recessional moraine looking upvalley toward Hilda Glacier, Alberta, Canada. The glacier had wasted to a small size in the late twentieth century.
  	View downvalley, showing Little Ice Age moraines built by Hilda Glacier. The outermost lateral moraine (left foreground) marks the maximum Little Ice Age ice margin, 1870-90s. Some of the moraines retain a core of stagnant ice that is insulated by the cover of sediment. Photos © J.S. Aber.

• 1886-87: Known as the Winter of Blue Snow in the northern Great Plains of the United States (Laskin 2004). An estimated 10-12 million cattle died on the open range during a blizzard in January.

• 1888: An intense winter storm, known as the Children's Blizzard, swept across the northern Great Plains of the United States on January 12 (Laskin 2004). It was one of the most sudden and severe cold spells the United States ever experienced, and the cold wave pushed southward all the way to Veracruz, Mexico. An estimated 250-500 people died in the northern United States, many of them children.

• 1890: Eyjabakkajökull, an outlet glacier of Vatnajökull (Iceland), surged to its maximum historical limit.

• 1890: Approximate end of Little Ice Age climate in Svalbard based on lake sediments (Jiang et al. 2011).

• 1900: Sléttjökull, an outlet glacier of Mýrdalsjökull (Iceland), stood at its Little Ice Age maximum. Other Icelandic glaciers at or near their maxima.

  View from margin of Sléttjökull looking northward over the recently deglaciated landscape. At the beginning of the twentieth century, the margin of Sléttjökull was located at the end moraine (yellow dots) in the middle distance, about 2 km from the present ice margin. Photo © by J.S. Aber.

• Early 1900s: Rapid retreat by glaciers on Mt. Kenya, Africa.

• 1917: Iceland became an independent sovereign state; gained full independence from Denmark in 1944.

• 1920: Marked decrease in sea ice in coastal waters of Iceland. Summer temperature rises markedly in the French Alps (Corona et al. 2011).

• 1920-30s: Glaciers declined rapidly everywhere, except Antarctica; end of Little Ice Ages.

  During the 1930s, Nigardsbreen (Norway) retreated rapidly and uncovered a rock basin in which this proglacial lake is ponded. A lateral moraine from an earlier retreat phase is visible above the lake in the right foreground. Photo © J.S. Aber.

• Early 2000s: Global warming continues. Glaciers in rapid retreat everywhere; some small glaciers have disappeared and many more will within the next few decades. Likewise ice caves are losing ice mass quickly in many situations.

  	Small glacier in the Trans-Ili Alatau mountains, Ile-Alatau National Park, Kazahkstan. Smooth snout shows rapid ablation in this mid-summer view. Photos © courtesy of Z. Andereck (ESU alumnus).
  	Demänovská Ice Cave in central Slovakia. Left: ice flow with mounds. Note people in upper left corner for scale. Right: small mound of ice on cave floor. Ice mound is ~1 m across. Ice masses in this cave have dwindled significantly during recent decades, as entrances are open in the summer. Photos © J.S. Aber.

Grapes and climate

The following chronology indicates a close correspondence between wine harvest dates and glacier advances during the Little Ice Age. Grape yield correlates most closely with mid-summer temperature. Early wine harvests generally coincided with glacier retreats; late harvests were times of glacier advances. However, glacier responses usually lagged 5-7 years behind the climatic changes indicated by wine harvest dates (Pfister 1981). Chronology of wine harvest dates and climatic conditions in western Europe is based on Le Roy Ladurie (1971).

• 1510-1559: Decidedly warm overall, average harvest date 26 Sept.
  
• 1560-1600: Definitely cooler, average harvest date 30 Sept. 1590s was coldest decade of 16th century.
  
• 1601-1616: Warm or average conditions, average harvest 25 Sept.
  
• 1617-1650: Outstanding cold episodes with low temperatures and late wine harvests.
  
• 1651-1686: Early wine harvest dates with drought episodes.
  
• 1687-1703: Late wine harvests, exceptionally cold spring/summer temperatures (thermometer readings). 1690s was coldest decade of seventeenth century, crop failures common.
  
• 1711-1717: Cold spring/summer weather, late wine harvests.
  
• 1718-1737: Warm spring/summer weather, early wine harvests.
  
• 1739-1752: Cold spring/summer weather, late wine harvests.
  
• 1757-1763: Warm spring/summer weather, early wine harvests.
  
• 1765-1777: Especially cold, wet spring/summer weather, low barometric pressure, late wine harvests.
  
• 1778-1784: Warm spell throughout Europe, highest thermometer readings recorded prior to twentieth century.
  
• 1801-1811: Hot summers, early wine harvests.
  
• 1812-1817: Cold, wet spring/summer weather. 1816 coldest year on record, latest wine harvests ever known (early November), cereal crops failed.
  
• 1850-1856: Cold springs and cool summers, late wine harvests.
  
• post-1856: Warm, clear spring/summer weather, high air pressure, early wine harvests, end of Little Ice Ages in western Europe.

During the late twentieth and early twenty-first centuries, global warming has impacted vineyards and wine production. When to harvest grapes for a fine wine is a delicate balance between three factors (Nicholas 2015):

1. Acid content – gradually decreases to a low level as grapes mature and ripen.
   
2. Sugar content – gradually increases to a high level as grapes mature and ripen.
   
3. Flavor potential – reaches a peak at grape maturity then begins to decline.

For optimal grape ripeness and wine flavor, all three factors achieve best balance in about three to four months depending mainly on summer temperature. Higher temperature speeds ripening and leads to grapes with higher sugar content. Furthermore, highly acclaimed vintage wines are often produced in years that are dry in the month before harvest, which explains why dry-summer Mediterranean climate is favorable.

The grape ripening process is highly sensitive for the thousands of varieties of Vitis vinifera grapes, each of which has unique conditions of soil and climate. For example, Pinot Noir and Riesling grapes prefer cool climate, whereas Cabernet is a warm-climate grape.

The Tokaj region is famous for a special white wine based on the Furmint grape variety. Most of the region is in Hungary with a small portion in the southeastern corner of Slovakia (shown here). Vineyards extend across southern slopes of the Zemplinske hills (left). Individual fields form intricate patterns on the landscape (right). Kite aerial photos © JSA & SWA.

The eventual result of this trend is possible relocation of vineyards into cooler climates at higher altitudes or latitudes. For example, southern Australian vineyards are moving into Tasmania. Oregon and Washington may gain new vineyards at the expense of California. Likewise in Europe, wine production may gradually shift from traditional regions in Spain, southern France, Italy, and Hungary to southern England as well as northern France, Belgium, Germany and southern Poland. However, these changes are not likely to take place quickly, as developing a vineyard and producing high-quality wine take many decades to perfect the grapes and production techniques.

Röbller Vineyard located on a hill top with 18 acres of grapes in the Missouri wine district. Several French-hybrid varieties are grown as well as the Norton, an American grape derived from Vitis aestivalis. This vineyard was established in 1988 and, thus, is still relatively young. See Röbller Vineyard. Kite aerial photo © SWA & JSA.

Most trees respond to temperature, namely length of winter cooling and spring warming, to trigger leaf emergence, although this may be highly variable among different species. The consequences of this are far reaching as wildlife, particularly migrating birds, may not be able to adjust their schedules to the availability of insects and other food dependent upon early leaf emergence.

Bottomland (floodplain) forest in the Missouri River valley at Ft. Leavenworth, Kansas. Left: after early spring burning of the forest understory, cottonwood trees in the foreground show green flowers and leaves in this April scene. Right: cottonwood trees have dropped most leaves, while other deciduous trees still hold a mix of green and colored leaves in mid-October. The green stripe across the middle is a former channel of the Missouri River. Kite airphotos by JSA and ESU students.

Oak forest at Woodson State Fishing Lake and Wildlife Area, southeastern Kansas. Part of the Cross Timbers ecoregion, this forest is characterized by black jack oak and post oak. This early November view shows autumn tree color ranging from green and yellow to gold and red, as trees hold leaves well into the fall season. Blimp airphoto by SWA and JSA.

Return to geospectra.net academic webpages. © J.S. Aber (2021).