Arctic sea ice reached its second-lowest July extent on record, according to new satellite data. Scientists say unusually warm air and ocean temperatures drove the rapid melt.

What happened

Less ice means darker water absorbs more heat, which speeds up warming further.

Why it matters

Researchers will watch September closely, when the ice usually reaches its yearly minimum.

Key facts

• Arctic sea ice reached its second-lowest July extent on record, according to new satellite data.

• Less ice means darker water absorbs more heat, which speeds up warming further.