NH Snow Cover Extent
|October 2017||Snow Cover Extent||1981-2010 Anomaly||Trend
(out of 50 years)
|million km2||million mi2||million km2||million mi2||million km2||million mi2||Year(s)||million km2||million mi2|
Data Source: Global Snow Laboratory, Rutgers University. Period of record: 1967–2017 (50 years)
The Northern Hemisphere snow cover extent (SCE) for October 2017 was 21.17 million square km (8.17 million square miles), which was 3.63 million square km (1.40 million square miles), or 20.7 percent, larger than the 1981-2010 average. This was the ninth largest October SCE in the 50-year period of record for the Northern Hemisphere. Each of the last six Octobers, beginning with October 2012, has seen above-average Northern Hemisphere SCE values. Despite the above-average monthly SCE, this was the smallest October value since since 2013. October's long term trend (since 1967) is +2.1% more SCE per decade, the largest such upward trend of any month.
The October North American SCE was 9.12 million square km (3.52 million square miles), 1.07 million square km (410,000 square miles) above average and the seventh largest on record. This is the sixth consecutive October with above average North American SCE. Snow cover was above average for much of Canada, interior Alaska, and parts of the U.S. High Plains. Below-average SCE was observed in western Alaska, parts of the southern Canadian Rockies, and northern U.S. Rockies to northern High Plains. The contiguous U.S. SCE was the 17th largest on record, the Canadian SCE was the sixth largest on record, while the Alaskan SCE was the 19th largest.
The Eurasian SCE during October was 12.05 million square km (4.65 million square miles), which is 2.55 million square km (0.98 million square miles) above average. This was the 11th largest October SCE on record for Eurasia. Above-average SCE was observed across much of Asia, and was particularly so across most of Russia, Scandinavia, central China, northern Mongolia, and northern Kazakhstan. Below-average SCE was observed across Tibet, and parts of the Hindu Kush mountains.
Sea Ice Extent
|October 2017||Sea Ice Extent||
(out of 39 years)
|million km2||million mi2||Year(s)||million km2||million mi2|
Data Source: National Snow and Ice Data Center (NSIDC). Period of record: 1979–2017 (39 years)
According to the National Snow and Ice Data Center (NSIDC), the Northern Hemisphere (Arctic) sea ice extent — which is measured from passive microwave instruments onboard NOAA satellites — averaged for October 2017 was 6.71 million square km (2.59 million square miles), 1.64 million square km (633,000 square miles), or 19.6 percent, below the 1981-2010 average. This was the fifth smallest October Arctic sea ice extent on record and 820,000 square kilometers (320,000 square miles) above the record low October extent set in 2012. The overall expansion of sea ice was faster than average throughout the month, but sea ice extent continued to be below-average throughout much of the Arctic, particularly in the Chukchi, Kara, and Barents Seas. Since 1979, October Arctic sea ice extent is decreasing at an average rate of 9.1 percent per decade.
The October Southern Hemisphere (Antarctic) sea ice extent was 17.70 million square km (6.83 million square miles), which was 400,000 square km (160,000 square miles), or 2.21 percent, below the 1981-2010 average. This was the fifth smallest October Southern Hemisphere sea ice extent on record. Southern Hemisphere October sea ice extent is increasing at an average rate of 0.7 percent per decade. On October 11 and 12, the Antarctic sea ice extent reached its annual maximum extent at 17.98 million square km (6.96 million square miles). This was the second smallest Antarctic sea ice extent maximum on record — only slightly larger than the maximum extent in 1986. The date tied with 2002 as the latest date of occurrence of the annual maximum.
For further information on the Northern and Southern Hemisphere snow and ice conditions, please visit the NSIDC News page.