Date : 20/10/2023

Relevance – GS Paper 1 - Geography

Keywords – LIA, BSIP, ITCZ, ISM

Context

A recent study challenges the conventional perception of the Little Ice Age (LIA) as uniformly cold and dry, revealing significant rainfall variations between CE 1671-1942. Conducted by the Birbal Sahni Institute of Palaeosciences (BSIP) in Karnataka, India, the research sheds light on the moist conditions during the LIA.

Methods: Core Sampling and Analysis

Scientists collected core sediment samples from Honnamana Kere Lake in Karnataka and analyzed pollen content to reconstruct vegetation-based climate change from CE 1219-1942. The study primarily focused on moist/semi-evergreen–dry tropical deciduous forests.

Findings of Recent Study:

Moist Little Ice Age (LIA) in Western Ghats

• The research shows a moist LIA in the Western Ghats, possibly due to increased Northeast Winter Monsoon (NEM). This wet period contrasts with prevailing assumptions about LIA's climate, highlighting the hydro-climatic contrast during this time.

Northward ITCZ Movement and Solar Activity

• The study attributes the climate change and heightened Southwest Monsoon (SWM) to the northward shift of the Inter Tropical Convergence Zone (ITCZ), positive temperature anomalies, increased sunspot numbers, and high solar activity. These factors contribute to the weakened Indian Summer Monsoon (ISM) during the LIA.

Implications and Future Research:

• The high-resolution palaeoclimatic records offer valuable insights for developing paleoclimatic models. Understanding the LIA's climatic variability aids in predicting future climate trends. This knowledge is vital for informed policy planning and understanding present and future ISM-influenced climatic conditions.

What is the Little Ice Age?

The Little Ice Age (LIA) was a climatic period spanning from the early 14th century to the mid-19th century. During this time, glaciers in various regions, such as the European Alps, New Zealand, Alaska, and the southern Andes, expanded. Across the Northern Hemisphere, mean annual temperatures decreased by 0.6 °C (1.1 °F) compared to the average temperature between 1000 and 2000 CE. The term "Little Ice Age" was coined by Dutch-born American geologist F.E. Matthes in 1939. Initially, it referred to the Earth's most recent 4,000-year period of glacier expansion and retreat. Today, some scientists use the term to describe the period between 1500 and 1850 when glaciers reached their maximum extent. However, it is more commonly used to denote the broader period from 1300 to 1850. The Little Ice Age followed the Medieval Warming Period (around 900-1300 CE) and preceded the current warming period that began in the late 19th and early 20th centuries.

Geographical area of Little Ice Age

Data from proxy records, such as ice cores, lake sediment cores, coral samples, and historical documents dating to the Little Ice Age, reveal diverse climatic conditions. While certain regions like western Greenland, Scandinavia, the British Isles, and western North America experienced cooler periods, with temperatures dropping 1 to 2 °C (1.8 to 3.6 °F) below the thousand-year averages, these declines rarely occurred simultaneously. Cool episodes also affected the Southern Hemisphere, leading to glacier advances in places like Patagonia and New Zealand, although not in sync with Northern Hemisphere events. Some regions, like eastern China and the Andes, remained relatively stable during the Little Ice Age.

Additionally, the era saw extended periods of drought, increased precipitation, and significant moisture fluctuations. Northern Europe faced long winters and short, wet summers, while parts of southern Europe experienced droughts and season-long heavy rainfall. Equatorial Africa and Central and South Asia endured multi year droughts.

Therefore, the Little Ice Age, while associated with cold temperatures, is best characterized as a period marked by heightened temperature and precipitation variability across various parts of the world.

Causes of Little Ice Age

The exact causes of the Little Ice Age remain uncertain, but scientists propose several factors that might have contributed to its onset and duration.

Variability in Solar Output:

• Low sunspot activity, indicating reduced solar output and less energy reaching Earth's surface, has been associated with colder periods. Two distinct periods of low sunspot activity, the Spörer Minimum (1450–1540) and the Maunder Minimum (1645–1715), coincided with the coldest years of the Little Ice Age in parts of Europe. While some scientists attribute the phenomenon to reduced solar radiation, this explanation does not account for brief cooling episodes observed in other regions during the same period, suggesting that reduced solar output alone cannot explain the Little Ice Age.

Changes in Atmospheric Circulation:

• Many scientists believe that the Little Ice Age in Europe was influenced by a shift in the North Atlantic Oscillation (NAO), a significant atmospheric-circulation pattern over the North Atlantic region. Changes in the NAO's positive and negative phases, affecting the track of North Atlantic storms, could explain climate variability and colder-than-normal conditions in certain European areas during the Little Ice Age.

Increased Volcanic Activity:

Explosive volcanic eruptions, such as the ones at Laki in Iceland (1783) and Tambora on Sumbawa Island (1815), played a role in the Little Ice Age. These eruptions propelled gases and ash into the stratosphere, reflecting solar radiation and leading to lower average temperatures worldwide for a few years. Some scientists suggest that these eruptions might have reinforced the negative phase of the NAO, causing cooler conditions in northern Europe. However, there is debate, as some scientists argue that such eruptions could be linked to warmer winter conditions in northern Europe.

In summary, the Little Ice Age likely resulted from a combination of factors, including variations in solar output, changes in atmospheric circulation patterns, and explosive volcanic activity. These factors interacted in complex ways, contributing to the climatic fluctuations observed during this period.

Effect of Little Ice Age on Civilization

Europe and North Atlantic Effects:

• Alpine glaciers advanced significantly, destroying farms, churches, and villages in Switzerland, France, and other areas.
• Cold winters and cool, wet summers caused crop failures and famines in northern and central Europe.
• Decline in North Atlantic cod fisheries due to falling ocean temperatures in the 17th century.

Greenland and Iceland Impact:

• Increased pack ice and storminess in the North Atlantic isolated Norse colonies in Greenland.
• Western Greenland colony collapsed due to starvation, and the eastern colony was abandoned.
• Iceland became more isolated from Scandinavia as sea ice expanded, encasing the island for longer periods each year.

North American Changes (1250-1500):

Native American cultures in the upper Mississippi valley and western prairies experienced a decline due to drier conditions, leading to a shift from agriculture to hunting.

Japan's Climate Shift:

• Glaciers have advanced in Japan.
• Mean winter temperatures dropped by 3.5 °C (6.3 °F).
• Summers were characterized by excessive rains and poor harvests.

Conclusion:

The Little Ice Age, spanning from the 14th to the mid-19th century, was a period of significant climate variability globally. Recent studies challenge the traditional perception of it being uniformly cold and dry, revealing diverse rainfall patterns and moist conditions in certain regions, such as the Western Ghats in India. The causes of this climatic phenomenon remain complex, involving factors like solar variability, atmospheric circulation changes, and explosive volcanic activity. The impact on civilizations was profound, leading to glacier expansions, agricultural challenges, and social disruptions across Europe, North America, and Asia. Understanding the multifaceted nature of the Little Ice Age is crucial for comprehending historical climate dynamics and its relevance in the context of present and future climate trends.

Source – PIB