Sea ice has retreated nearly four times as fast in the Chukchi Sea as the global average over the past four decades. Researchers have now found that melting sea ice is causing a loss of haul-out habitat among walrus populations along the Arctic coast, forcing large herds onto crowded beaches. They believe increased predation and stampede-related deaths on these crowded beaches to be the cause of rising walrus mortality in the region.

On the basis of the above passage, the following assumptions have been made:

1. Regions of sea ice warm faster than other regions due to global warming.

2. Global warming can lead to overcrowded beach conditions in some areas.

3. Melting sea ice can increase walrus mortality in some areas.

Which of the above assumptions is/are valid?