Question

the loss in sea ice can affect all the organisms in the arctic food web. what is the most likely cause for the loss of sea ice?
global warming
decrease in the sea level
phytoplankton respiration
increase in the number of polar bears

Explanation:

Global warming causes a rise in temperature. This increase in temperature leads to the melting of sea ice. A decrease in sea level would not cause sea ice loss. Phytoplankton respiration and an increase in polar bear numbers do not directly lead to sea - ice loss.

Answer:

global warming