The Arctic sea ice maximum

NSIDC scientists announced today that the Arctic sea ice cover has likely reached its maximum extent, marking the beginning of the melt season. (For details, see Arctic Sea Ice News & Analysis). What is the sea ice maximum and why does it matter?

The maximum ice extent marks the beginning of the melt season for Arctic sea ice. Leads, long cracks in the ice, begin to open up and the ice cover starts to melt as sunlight brings warmth to the Arctic. Credit: Angelika Renner

What is the maximum and when does it happen?
Arctic sea ice melts and regrows in an annual cycle, freezing throughout the winter months and melting in the spring and summer. The ice cover generally reaches its maximum extent sometime in late February or March. After that, ice melts through the summer, hitting a low point in early or mid-September. NSIDC scientist Walt Meier said, “The maximum marks the point when the Arctic shifts from a freezing period into the summer melting period.” Continue reading

What about sea ice in winter?

Researchers take measurements of the physical properties of sea ice in Fram Strait, in the Canadian Arctic. Thinner sea ice melts away faster in the summer compared to older, thicker ice. Credit: Angelika Renner

Arctic sea ice has most likely frozen to its maximum extent for the winter. This event marks the turning point between winter and spring for sea ice, and may affect the amount of ice that will remain by end of summer. In early April, NSIDC scientists will talk about what this year’s maximum signifies for the upcoming summer. Meanwhile, readers are asking how the ice cover this year is different from the ice cover in years past.

Arctic sea ice grows each winter, hitting its annual maximum sometime in March. When the sun returns to the Arctic in the spring, the air warms up and the ice starts to melt. The ice retreats through the warmer summer months, hitting its lowest point sometime in September. Although scientists watch the sea ice year-round, they pay attention to the highest and lowest extents of the year as indicators of the overall health of the sea ice. Continue reading