Polar ice is more than just frozen water – it is home to many creatures and affects the whole ocean ecosystem . Arctic foxes live on Arctic ice, penguins live on Antarctic ice, and seals live on both [4, 5]. Arctic wildlife is already feeling the effects of climate change, far more than the global average .
Polar bears find food (e.g. seals) on Arctic sea ice, and as more is lost, they will struggle to feed [1,2]. They will have to spend more time on land , potentially leading to interbreeding with grizzly bears  and increased conflict with humans . If Arctic sea ice is completely lost, polar bears as a distinct species will likely go extinct .
As Arctic ice melts, ships are taking more northerly routes . This could affect many species including whales by direct collision with ships, and noise pollution causing stress [7,8,9].
But melting sea ice doesn’t just affect big animals, it affects the whole marine food web. For example, as more ice bergs break off the Antarctic, the sea floor is being pounded more often by ice, reducing the life expectancy of creatures that live there .
Phytoplankton (like tiny plants) are at the bottom of the marine food chain, and many animals depend on them . When sea ice melts in summer (a natural phenomenon), nutrients are released into the water, which are used by phytoplankton to grow . Melting ice also exposes water to sunlight, which is used by the phytoplankton in photosynthesis [4,13]. This results in huge explosions of algae called “algal blooms”. So, as more ice melts, we might expect more algal blooms [11,13]. That’s good news so far. However, there are also negative effects. The natural cycles between freezing and melting mixes seawater at different depths, bringing nutrients up to the surface . With less water re-freezing each winter, there will be less mixing and so the surface water will be less nutrient-rich, likely making it harder for phytoplankton to grow [14, 15].
Melting ice has complex effects, but you now understand some of them. It will massively affect animals as small as single-celled phytoplankton up to polar bears and whales!
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