Sea ice extent in the Barents Sea and Fram Strait

Closeup of glacier ice.
Photo: Stein Ø. Nilsen / Norwegian Polar Institute

It is important to monitor the extent of sea ice because it is vital for the climate in the Arctic and globally, and because it sets important limits for the ecosystems in the Arctic. The sea ice extent in the Barents Sea and the Fram Strait is presented here. The extent in April is presented because it is usually at its maximum then, and in September, as that is when it is usually at its minimum. The data presented here derive from satellite monitoring, which began in 1979.

What is being monitored?

Sea ice extent

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The figure shows the sea-ice extent in April in the Barents Sea, the month that normally has the highest prevalence of ice in the area. Data are shown as monthly mean values ​​for each year, 3 years running average values​, and linear trend throughout the period. The interannual variation is large, but there is also an obvious negative trend for April through the period. The lowest record of extent was observed in April 2016. The 2018 data are based on preliminary numbers. Hence, minor adjustments can be made when data from 2018 are re-analysed.

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The figure shows the ice extent in September in the Barents Sea, the month when the sea-ice extent is normally at its lowest in the area. Data are shown as monthly mean values ​​for each year, 3 years running average values, and linear trend throughout the period. September shows a negative trend throughout the period, but interannual variations are also large. The lowest extent for September was observed in 2013. The 2018 data are based on preliminary numbers. Hence, minor adjustment can be made when data from 2018 are re-analysed.

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The figure shows the ice extent in the Fram Strait in April, the month that normally has the largest extent of ice here. The data are shown as monthly mean values for each year, 3 years running average values, and linear trend throughout the period. The year-to-year variation is large, but there is also a distinct negative trend for April throughout the monitoring period. 2004 was an absolute minimum for April ice in the observation period. The 2018 data are based on preliminary numbers. Hence, minor adjustment can be made when data from 2018 are re-analysed.

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The figure shows the ice extent in the Fram Strait in September, the month when the extent normally is at its lowest. The data are shown as monthly mean values for each year, 3 years running average values, and linear trend throughout the period. The year-to-year variation is large, but there is also a distinct negative trend for September throughout the monitoring period. In 2004, the September ice extent was at its absolute minimum in the observation period. The 2018 data are based on preliminary numbers. Hence, minor adjustment can be made when data from 2018 are re-analysed.

Status and trend

Many scientific publications document the decrease in the sea-ice extent in the Arctic, and many studies have shown that the most dramatic changes have been in the Russian part of the Arctic, in the Barents Sea.

The sea-ice extent in the Barents Sea is calculated in a box delimited by 72°N and 82°N and longitudes 10°E and 60°E. In the Fram Strait, it is calculated in a box delimited by 70°N and 82°N and longitudes 20°W and 15°E. In most years, the maximum extent of sea ice in the Barents Sea is in April, and the minimum in September. The minimum and maximum months vary somewhat more in the Fram Strait, but MOSJ has chosen to display the same months here as for the Barents Sea.

The Barents Sea is characterized by great variation from year to year. The main development in the ice extent during the monitoring period has been a clearly negative trend.

Based on a least-squares linear regression, the rates of decadal decrease in April and September were -9.5% and -16.0%, respectively. The time series (1979–2018) for the ice extent in April shows 5 years (1979, 1981, 1987, 1998 and 2003) with distinctly high values and 6 (2006, 2007, 2008, 2012, 2015 and 2016) with distinctly low values. In September, there are 5 years (1982, 1989, 1993, 2003 and 2014) when the ice extent in the Barents Sea was particularly large and nine years (1979, 1984, 1996, 2001, 2004, 2011, 2012, 2013 and 2018) when it was especially small. The greatest extent of sea ice throughout the period was measured in April 1981 and the least in September 2013.

The ice extent in the Fram Strait also varies greatly from year to year. Both April and September show a declining trend during the monitoring period. The year when the ice extent was at its maximum in April, 1986, was 2 years after a marked decrease in the April extent in 1984. Since then, the pattern has generally been that years with an above average ice extent succeed years with a below average ice extent, and the year-to-year variation has decreased. The minimum extent in April was in 2004.

In September, the ice extent varies considerably from year to year throughout the period. The minimum extent in September was in 2004.

Based on a least-squares linear regression, the rates of decadal decrease in April and September were -7.0% and -10.0%, respectively.

Causal factors

Higher sea and air temperatures result in less sea ice. A declining trend in the ice cover over large parts of the Arctic has been seen ever since satellite measurements began in 1979. As the ice extent in the Fram Strait is also strongly affected by processes in the Arctic Ocean, the ice extent in the Barents Sea is a more robust indicator for climate development. Ocean currents and precipitation also influence the sea ice, but within such large areas as the indicator covers, isolated events of a local nature will have a minimum effect over time.

Consequences

Sea ice plays an important role for the radiation balance on the Earth. Snow-covered sea ice can reflect almost 80% of the incoming solar energy, whereas open water absorbs 90%. Warming of the Arctic can thus lead to melting of the sea ice, which in turn results in more energy being taken up and the Arctic becoming still warmer.

In addition, some ecosystems and species are entirely dependent upon the sea ice. Some marine organisms live only in ice-covered waters, and whales, seals and polar bears are dependent upon the ice in their life cycles.

About the monitoring

It is important to monitor the sea-ice extent because it is vital for the climate in the Arctic and globally, and because it sets important limits for the ecosystems in the Arctic. Since monitoring by satellite monitoring started in 1979, a declining trend for the sea-ice extent in the Arctic is observed. Monitoring is important because conditions for sea ice are a key indicator for measureing the rate of climate change, and positive feedback mechanisms are also connected to the extent of sea ice. A reduction in sea ice changes the Earth’s radiation balance and can alter or displace the arctic ecosystems.

Places and areas

Relations to other monitoring

Monitoring programme
International environmental agreements
Voluntary international cooperation
Related monitoring