Lecture 3: Global Impacts of Arctic Changes

Introduction

• Third lecture in the series on cryosphere.
• Focus on global impacts of Arctic changes.
  • Sea ice extent and permafrost thaw's impact on global climate.
  • Land ice changes and sea level rise.

Ice-Albedo Climate Feedback Loop

• Ice reflects sunlight, keeping Earth cool (high albedo).
• Negative feedback: Ice stabilizes temperature despite small increases.
• Positive feedback: Loss of sea ice leads to more heat absorption by oceans (low albedo).
  • Concerns about a runaway effect were present, but simulations suggest no tipping point for Arctic sea ice.
  • Winter cooling allows for regrowth of ice.

Permafrost Carbon Climate Feedback Loop

• Arctic soils are frozen, decomposition is slow.
  • Accumulation of carbon-rich plant detritus in permafrost.
• Permafrost contains more carbon than the Amazon.
• Thawing makes carbon-rich soils available for decomposition.
  • Anaerobic conditions lead to methane emission, a potent greenhouse gas.
  • Potential for methane emissions to vastly increase.

Impact of Plant Growth

• Warming increases plant growth (Arctic greening).
  • More CO2 absorbed, can counter methane emissions.
  • Debate on whether CO2 absorption or methane emission will prevail.

Glacier Ice Loss and Sea Level Rise

• Sea level rise at ~1/8 inch per year due to glacier ice loss.
  • Storm surges and flooding risks increase.
• Thermal expansion of oceans also contributes to sea level rise.
• Potential runaway process with ice shelves and glaciers.
  • Warm ocean water melts ice shelves, accelerating glaciers.
  • Concerns for ice cliff collapse causing rapid ice loss.

Conclusion

• Changes in cryosphere have significant global impacts.
  • Feedback loops contribute to climate warming.
  • Sea level rise from ice melt is a major concern.
• Close monitoring of these changes is essential.