Two New Studies Find Thwaites Glacier Melt Cannot Be Driven By Human Activity Or A Warming Ocean

When a human math expert won’t do the math, ask Gemini.

I asked it what the Antarctic Circle latitude was in 1940 and today, the distance between those latitudes, and the total surface area between them.

In 1940, the mean latitude of the Antarctic Circle was approximately 66°33′10.5″ S, while today it is approximately 66°33′50.7″ S. That’s a poleward movement of 1.25 kilometers, or a total area of about 19,773 square kilometers.

Then I asked for the extremes, and if the numbers were different for Arctic and Antarctic.

“The predicted minimum and maximum latitudes, distances, and areas are exactly identical for both the Arctic and Antarctic Circles, as they are both driven symmetrically by the same axial tilt (obliquity) cycle of the Earth. [1]
Because the Earth’s axial tilt fluctuates between a minimum of 22.1° and a maximum of 24.5° over a 41,000-year Milankovitch cycle, the boundaries of the polar circles shift accordingly. [1, 2]
Latitudes and Extremes

• Minimum Latitude (Closest to the Equator): 65.5° N (Arctic) and 65.5° S (Antarctic). This occurs when the Earth is at its maximum axial tilt of 24.5°. [1]
• Maximum Latitude (Closest to the Poles): 67.9° N (Arctic) and 67.9° S (Antarctic). This occurs when the Earth is at its minimum axial tilt of 22.1°. [1]

Distance Between Extremes
The total meridian (north-south) distance between these two geographic extremes is 2.4 degrees of latitude, which translates to approximately 267 kilometers (166 miles).
Total Surface Area Affected
The total surface area inside this shifting buffer zone in each hemisphere is approximately 4,225,211 square kilometers (1,631,362 square miles).
To put this vast area into perspective:

• The moving band in the north or south hemisphere is roughly the size of the entire Indian subcontinent or the combined area of Alaska, Texas, and California.
• Cumulatively, this means that over thousands of years, more than 8.4 million square kilometers of Earth’s surface transitions back and forth between experiencing true polar conditions (like the 24-hour midnight sun) and subpolar conditions.”

There ya go. More data to input into climate calculations, especially regarding the Arctic and Antarctic border zones.

I suspect it’s considering Earth as a perfect sphere, so I ask. It gives corrections.

No, the previous numbers did not account for the Earth’s flattening and were based on a perfect sphere with a mean radius of 6,371 kilometers.
Because the Earth spins, it bulges at the equator and flattens at the poles (an oblate spheroid). When we use the precise WGS-84 ellipsoidal model used by modern GPS systems, the numbers change slightly because the surface curves differently near the poles.
Here is how accounting for the Earth’s true shape alters the calculations:
Spheroid vs. Sphere Comparison
MetricPerfect Sphere AssumptionTrue Oblate Spheroid (WGS-84)The DifferenceDistance between extremes~266.9 km (165.8 miles)267.6 km (166.3 miles)+0.7 km (0.5 miles)Total Area of one polar zone~4,225,223 km²4,254,226 km²+29,003 km² (+11,198 sq miles)
Why the numbers increase near the poles
It seems counterintuitive that a squashed planet results in a larger distance and surface area near the poles, but it comes down to two geometric factors:

1. Meridian Stretching: Because the Earth is flatter at the top and bottom, the surface curve is less sharp. A flatter curve means you have to travel a slightly longer physical distance along a meridian line to change your latitude by exactly 1 degree.
2. Flattened Geometry: The surface area formulas for an ellipsoid redistribute the total area slightly differently than a sphere, resulting in an additional 29,000 square kilometers (roughly the size of Belgium) being affected by this polar drift in each hemisphere.