Why does sea ice near Alaska and the Bering Strait make the Pacific exit difficult?

The Pacific exit of the Northwest Passage is considered difficult primarily due to the persistent presence of sea ice and the influence of the polar ice cap.12

The challenges at this exit include:

• Ice Pressure: The polar ice cap presses down on the shallow north coast of Alaska for much of the year, which funnels large masses of ice into the Bering Strait.1
• Ice Thickness and Drift: During winter, the region is covered by ice fields that can reach 4 to 5 feet in thickness, with hummocks sometimes exceeding 100 feet in height. Even in midsummer, drift ice often remains in the Bering Strait, creating hazardous conditions for navigation.23
• Severe Weather: The area is subject to frequent and severe winter storms that can coat ship superstructures with ice, alongside powerful tidal currents and poor visibility caused by fog and rain.23

While global warming has led to a decline in sea ice coverage and thickness in recent years, these environmental factors have historically made the Pacific exit a formidable maritime challenge.415