Possible Clues:

• Like Peary's explorations
• A kind of bear
• Regions within the Arctic and Antarctic Circles
• Word with cap or opposite
• With 3-Down, extremes, and a hint to this puzzle's theme
• — Bear; — circle
• Word before 'opposites' or 'vortex'
• Word before 'bear' or 'opposite'
• Diametrically opposed — very cold
• Of extreme opposites