Snow on Arctic Sea Ice in a Warming Climate as Simulated in CESM

Area of Science:

• * Climate Science
• * Arctic System Science
• * Earth System Modeling

Background:

• * Earth system models are crucial for projecting Arctic snow-ice system responses to climate change.
• * Understanding snow on Arctic sea ice is vital for accurate climate feedback assessments.

Purpose of the Study:

• * To evaluate the realism of the Community Earth System Model (CESM) in simulating snow on Arctic sea ice.
• * To assess how snow conditions on Arctic sea ice may change under different climate forcing scenarios.

Main Methods:

• * Comparison of in situ, airborne, and satellite observations with CESM versions 1 (CESM1-LE) and 2 (CESM2).
• * Evaluation of snow depth, distribution, accumulation, melt timing, and trends across model versions.
• * Analysis of future snow conditions under the SSP5-8.5 forcing scenario using CESM2.

Main Results:

• * CESM2 underestimates snow depth and exhibits overly uniform snow distribution, with unrealistic accumulation and melt timing.
• * CESM1-LE simulates excessively thick and variable snow cover.
• * CESM2 projects earlier spring melt, reduced summer-autumn accumulation, increased sublimation, and more snow-ice formation under SSP5-8.5.

Conclusions:

• * Both CESM1-LE and CESM2 exhibit biases in simulating Arctic sea ice snow cover, affecting climate projections.
• * CESM2 suggests snow-free ice summers may precede an ice-free Arctic by several decades, potentially accelerating melt.
• * Accurate representation of snow on Arctic sea ice is critical for improving Earth system model predictions of climate change impacts.