PREVAILING CLIMATIC TRENDS PERSPECTIVE AND ITS IMPACTS ON GLACIERS IN CENTRAL KARAKORAM, PAKISTAN

Technical Summary: Prevailing Climatic Trends and Impacts on Glaciers in Central Karakoram, Pakistan

Problem Statement
The Hindukush-Karakorum-Himalaya (HKH) region, often termed the "Third Pole," is critical for water security in the Indus Basin. While global warming typically drives glacier retreat, the Central Karakorum region exhibits a contrasting phenomenon known as the "Karakoram Anomaly," where glaciers show stability, expansion, or surging rather than retreat. The precise climatic drivers behind this anomaly remain poorly understood due to a scarcity of long-term, high-altitude in-situ meteorological data and the region's rugged, inaccessible terrain. This study addresses the gap in understanding the specific climatic variability trends in the Central Karakoram and their direct correlation with the stability of the Barpu glacier.

Methodology
The research employed a multi-faceted approach combining meteorological data analysis, field glaciological measurements, and socio-scientific inquiry:

• Meteorological Data: The study analyzed long-term climate data from two distinct stations:
  • Gilgit PMD Station (Valley Floor): Data spanning 1986–2015.
  • WAPDA Ziarat Station (High Altitude): Data spanning 1995–2020.
  • Parameters: Annual and seasonal trends of mean maximum/minimum temperature, precipitation, relative humidity (R/H), and solar radiation (SR).
  • Statistical Analysis: Trends were assessed using Kendall's tau-b test to determine significance.
• Glaciological Fieldwork: Ground observations were conducted on the Barpu glacier (located in the Hunza sub-basin) to measure the snout coordinates and the thickness of supra-glacial debris in the ablation zone.
• Indigenous Perception: A questionnaire study was conducted in 2013 and 2022 with local elders to record historical observations of climate variability and glacier behavior over the last three decades.

Key Results
The analysis revealed distinct climatic trends that differ from global warming patterns, particularly at high altitudes:

• Temperature Trends:
  • Gilgit (Valley): Annual mean temperatures showed an increasing trend. However, seasonal analysis indicated a decline in maximum temperatures during summer and autumn, with increases in spring and winter.
  • Ziarat (High Altitude): Annual mean maximum temperatures showed a declining trend, while mean minimum temperatures increased. Crucially, seasonal maximum temperatures declined in summer, winter, and autumn, with a rise only in spring. Minimum temperatures decreased in winter and summer but increased in spring and autumn.
• Precipitation: Both stations recorded an increasing trend in total annual precipitation. Seasonal data confirmed increases across all seasons (winter, spring, summer, and autumn) at both locations.
• Solar Radiation (SR): A significant declining trend was observed in mean annual solar radiation at the high-altitude Ziarat station. This decline was consistent across all seasons except spring.
• Relative Humidity (R/H): There was a marked increasing trend in both mean annual maximum and minimum relative humidity at the high-altitude station. This increase was observed across all seasons.
• Glacier Status (Barpu Glacier):
  • Debris Cover: The mean thickness of supra-glacial debris in the ablation zone was measured at 1–1.5 feet.
  • Snout Stability: GPS coordinates taken in 2013 and 2022 confirmed no distinct fluctuation in the glacier snout.
  • Local Perception: Indigenous inhabitants reported that the Barpu glacier is retreating slowly or is stable, with no considerable changes observed over the last two to three decades.

Key Contributions

• Validation of the Karakoram Anomaly: The study provides empirical evidence supporting the existence of the Karakoram Anomaly in the Central Karakoram, demonstrating that glaciers in this specific region are responding differently to global climate drivers compared to the broader HKH region.
• Climatic Drivers of Stability: The research identifies a specific combination of climatic factors facilitating glacier stability:
  • Reduced Ablation: Declines in summer, winter, and autumn temperatures, coupled with reduced solar radiation (particularly in summer), have lowered the melting rate.
  • Enhanced Accumulation: Increased precipitation across all seasons, particularly winter and spring, has contributed to mass gain.
  • Humidity Effects: Increased relative humidity and cloud cover (indicated by reduced SR) have likely decreased sublimation and evaporation rates, further protecting the ice mass.
• Role of Debris: The study highlights the protective role of the 1–1.5 feet thick debris cover, which insulates the glacier surface and further reduces melting rates.

Significance
The paper concludes that the Barpu glacier in the Central Karakoram exhibits stable or low-melting behavior, contrasting with the widespread retreat observed in the Eastern Himalayas. This stability is attributed to a synergistic effect of decreasing summer temperatures, reduced solar radiation, and increasing precipitation and relative humidity. These findings suggest that the "Karakoram Anomaly" is driven by local climatic shifts that favor accumulation over ablation. The study underscores the importance of high-altitude meteorological data in understanding regional cryospheric responses, noting that valley-floor data alone may not fully capture the dynamics driving glacier stability in high-elevation environments. The authors assert that these diverse responses to global warming necessitate region-specific assessments rather than applying generalized global warming models to the entire HKH range.