Arctic Route Accessibility Analysis
Measured how many months a year Arctic shipping routes are actually open, using observed NSIDC sea-ice concentration grids from 1979 to 2025, and translated the result into distance saved on the Busan–Rotterdam leg.
Quick read
The through-line of the work.
Open
The starting question
There is plenty of talk about shrinking ice, but it was hard to find anything that says in numbers how many months a ship can actually get through. So I fixed the target metric first: navigable months per year.
Build
What I checked
I laid a 50 km buffered corridor over each great-circle route onto the sea-ice grid and computed mean ice concentration and a 95th-percentile bottleneck value for every segment.
Turn
What changed my view
I did not report trends from OLS alone. Sea-ice data spikes in particular years, so I ran Theil-Sen robust regression alongside it and accepted a result only when both methods agreed in sign.
Close
Where I draw the line
What remained was not a statement that the Arctic has warmed but two numbers: about 3.4 months a year open to ice-1A/PC7-class vessels, and still zero months on the Transpolar route over the Pole.
01 · Start
The question I began with
How much has sea-ice loss changed the operational window of Arctic routes, and what choice does that leave a Korean shipper?
02 · Material
The data and evidence
03 · Work
How I worked through it
- 01
Pin down provenance
Ingested NSIDC gridded GeoTIFFs, fixed provenance with a SHA-256 checksum manifest, and cross-checked gridded extent against the official NSIDC series.
- 02
Build route corridors
Buffered the great-circle tracks of the Northern Sea Route, Northwest Passage, and Transpolar route by 50 km, rasterised them onto the ice grid, and split them into segments for bottleneck detection.
- 03
Compute feasibility
Applied per-vessel-class concentration thresholds to decide navigability by year and month, identified the limiting bottleneck segment, and aggregated navigable months per year.
- 04
Validate trends and read scenarios
Ran OLS alongside robust Theil-Sen and reported a trend only when both agreed, then framed the distance saving against Suez as logistics and cruise scenarios.
04 · Takeaway
What the numbers suggested
For ice-1A/PC7 vessels the NSR navigable season grew from about 0 months a year in the 1980s to about 3.4 months a year since 2015, a robust +0.9 months per decade where OLS and Theil-Sen agree.
September corridor sea-ice concentration fell about 3.2% per decade.
The NSR is 3,151 nautical miles, about 29.8%, shorter than the Suez routing for Busan–Rotterdam.
The Transpolar route is the shortest on paper but recorded zero navigable months across the entire record for non-icebreaking vessels.
Not claimed
- Does not forecast future sea ice. Only past trends from observed grids.
- Does not claim commercial navigability. Insurance, ports, icebreaker support, and regulation are excluded.
- Does not claim domain expertise. GIS and climate data were explored with AI assistance.
05 · Use
Where this helps
Reduced the finding to two decision-grade numbers, navigable months per year and nautical miles saved, so routes can be compared on when and for how long they are usable.
06 · Boundary
What still needs checking
- •This is an observation-based analysis, not a climate model that forecasts future ice.
- •Navigability is judged on sea-ice concentration thresholds and excludes insurance, port, icebreaker-escort, and regulatory constraints.
- •Some risk and cost layers in the extended Phase E analysis use synthetic stand-ins where real data was unavailable; these are labelled explicitly in the code.
07 · Figures
Tables and figures
Mean navigable months per decade
Verified sourceDecade means recomputed from the project's own output table. Sampling covers June–November and counts a month as navigable when it clears the concentration threshold; it does not imply commercial viability.
Source · outputs/tables/nsr_annual_navigability.csv · NSIDC Sea Ice Index v4 (ice-1A/PC7)
Trend validation and distance saving
Verified sourceOLS slope
+0.92 months/decade
Theil-Sen slope
+0.83 months/decade
Fit · significance
R² = 0.66 · p < 0.001
Saving versus Suez
3,151 nm · 29.8%
A trend counts only when OLS and Theil-Sen agree in sign. The distance saving is computed on great-circle routings and excludes port access and operating cost.
Source · outputs/tables/trends_navigable_months.csv · outputs/tables/logistics_vs_suez.csv