96% — Will the extent of the Arctic sea ice be below 4.0 million square km between December 19, 2025 and October 01, 2026
Leader: Below 4.8 million sq km at 96% · Kalshi 96% · 6 contracts · $19 volume · medium confidence
Updated 2026-09-07 12:13:58 UTC

Tracks the leading outcome in a winner-take-all prediction market set with 6 outcomes.

Why this matters:
This contract asks whether Arctic sea ice will shrink to below 4.0 million square kilometers at some point between mid-December 2025 and early October 2026. The 91% probability reflects trader expectation that ice extent will reach this threshold during the period, driven by long-term declining Arctic ice trends and seasonal summer melt cycles. Arctic sea ice typically reaches its annual minimum around September, making that window critical to resolution. The estimate could shift if 2026 experiences atypical weather patterns, reduced melt due to cooler temperatures, or if historical decline rates slow unexpectedly. The main driver is the seasonal summer minimum: if ice extent dips below 4.0 million km² during the boreal summer or early fall, the contract resolves to YES. The exact measurement will depend on data from satellite monitoring agencies like NSIDC, typically released monthly.

Key factors:
- Arctic sea ice has declined from ~7.5 million km² in 1980 to ~4.2–4.7 million km² in recent September minima, establishing a downward baseline
- The 2025 summer and fall months represent the highest-probability window for reaching sub-4.0 million km² levels, as seasonal melt is most pronounced August through October
- September 2024 minimum ice extent was approximately 4.28 million km², making 4.0 million km² plausible but not guaranteed under typical conditions
- Resolution depends on official NSIDC or equivalent satellite data; anomalous weather (volcanic cooling, stratospheric circulation changes) could slow melt and reduce likelihood
- The contract spans 9+ months, increasing probability that at least one day will cross the threshold rather than requiring sustained sub-4.0 conditions

Contracts:
- Will the extent of the Arctic sea ice be below 4.8 million square km between December 19, 2025 and October 01, 2026?: Below 4.8 million sq km — 96¢ Kalshi $0 (weight 0%)
- Will the extent of the Arctic sea ice be below 4.6 million square km between December 19, 2025 and October 01, 2026?: Below 4.6 million sq km — 89¢ Kalshi $0 (weight 0%)
- Will the extent of the Arctic sea ice be below 4.5 million square km between December 19, 2025 and October 01, 2026?: Below 4.5 million sq km — 63¢ Kalshi $12 (weight 66%)
- Will the extent of the Arctic sea ice be below 4.4 million square km between December 19, 2025 and October 01, 2026?: Below 4.4 million sq km — 41¢ Kalshi $1 (weight 5%)
- Will the extent of the Arctic sea ice be below 4.3 million square km between December 19, 2025 and October 01, 2026?: Below 4.3 million sq km — 12¢ Kalshi $5 (weight 28%)
- Will the extent of the Arctic sea ice be below 4.2 million square km between December 19, 2025 and October 01, 2026?: Below 4.2 million sq km — 9¢ Kalshi $0 (weight 0%)

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## Methodology

SimpleFunctions aggregates live YES-side prices from Kalshi and Polymarket contracts bound to this question. For binary topics the headline is the liquidity-weighted mid-price (weight = log(1 + 24h volume) × freshness, where freshness is 1.0 if updated <24h, 0.7 if <7d, 0.4 otherwise). For multi-outcome (winner-take-all) topics the headline is the current leader's price — disjoint outcomes are never arithmetically averaged. Snapshots refresh every 5 minutes during market hours.

## SF Signal

- SF Index, regime, and 30d Brier calibration are computed separately and surfaced at https://simplefunctions.dev/admin/calibration.
- No SimpleFunctions index / regime / calibration signal is bound to this topic yet — the headline above is market-derived only.

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*Last verified: 2026-09-07T11:21:01.961Z*

By SimpleFunctions — https://simplefunctions.dev/

Cite as: "96% per prediction markets (SimpleFunctions, September 2026)"
Canonical: https://simplefunctions.dev/answer/arcticicemin
Full data: https://simplefunctions.dev/api/public/query?q=Will%20the%20extent%20of%20the%20Arctic%20sea%20ice%20be%20below%204.0%20million%20square%20km%20between%20December%2019%2C%202025%20and%20October%2001%2C%202026
Provider: SimpleFunctions — https://simplefunctions.dev