Ch.4 Polar Communities (pt.1)

Why is Antarctica colder than the Arctic?

it is at higher elevation and has no water underneath to buffer heat exchange

What are polynyas?

year-round areas of open water surrounded by sea ice

What causes polynyas?

ocean currents and upwelling of warmer water

Why are polynyas important for wildlife?

they act as refuges for air-breathing mammals

Why are polynyas highly productive in spring?

light can enter the water because there is no ice blocking it

What seasonal light extremes occur in polar regions?

nearly 24 hours of daylight in summer and 24 hours of darkness in winter

How do Antarctic seasons compare to the Northern Hemisphere?

Antarctic winter occurs during Northern Hemisphere summer, and vice versa

How are polar ecosystems different between the Arctic and Antarctic?

each pole has evolved unique ecosystems due to differences in geography, ice, and environment

What type of body of water is the Arctic Ocean?

a relatively small, isolated ocean

What major seafloor feature is found in the Arctic Ocean?

an extensive, shallow continental shelf

What surrounds the Arctic Ocean?

two major landmasses (Eurasia and North America)

What are the two main Arctic Ocean outlets?

Bering Strait (Pacific) and Fram Strait (Atlantic)

How does freshwater input affect the Arctic Ocean?

rivers create a low-salinity surface layer above denser salt water

What is the effect of river discharge on the Arctic seafloor?

it creates a soft bottom

How does Arctic sea ice change seasonally?

it expands in winter and retreats in summer

When is Arctic sea ice largest and smallest?

• largest in April

• smallest in September

Where does most Arctic sea ice melt occur?

over continental shelves

What happens to sea ice in the central Arctic?

it stays frozen and thicker

Why is sea ice porous?

it contains brine-filled channels that stay unfrozen

Why is sea ice important for ecosystems?

it allows algal communities to live inside the ice, supporting the food web

Where does high primary production occur in the Arctic Ocean?

within and under sea ice

What organisms are key primary producers in Arctic ice?

photosynthetic diatoms (ice algae)

What happens during summer ice melt?

algal blooms increase dramatically, boosting productivity

How does Arctic productivity support other organisms?

it supports marine mammals, seabirds, and benthic communities via sinking organic matter

When are ice-free Arctic summers predicted?

around the 2040s

How does melting Arctic ice affect sea level?

it contributes to global sea level rise

How could Arctic melting affect ocean circulation?

it may disrupt the Global Conveyer Belt by lowering salinity and preventing water from sinking

How does reduced ice affect primary production?

it increases sunlight, potentially increasing production

What ecosystem is lost with declining sea ice?

unique sea ice-dependent ecosystems

Which species are strongly impacted by ice loss?

ice-dependent breeders like polar bears

What human activities increase with less Arctic ice?

fishing, oil and gas drilling, and shipping routes

How is the Southern Ocean different in geography from the Arctic Ocean?

it is not landlocked; it surrounds Antarctica

What major freshwater input difference exists between the Arctic and Southern Ocean?

there is no low-salinity surface layer like in the Arctic

How does the absence of river input affect the seafloor in the Southern Ocean?

there is no river sediment, so the bottom is harder

What is the structure of continental shelves in the Southern Ocean?

they are narrower and steeper than in the Arctic

How does sea ice seasonality in the Southern Ocean compare to the Arctic?

it also has strong seasonal changes but sea ice almost disappears in summer