Figure 1. Daily Arctic sea ice extent on July 21 was 8.28 million square kilometers (3.20 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data. —Credit: National Snow and Ice Data Center
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Overview of conditions

On July 21, Arctic sea ice extent was 8.28 million square kilometers (3.20 million square miles). This is 617,000 square kilometers (238,000 square miles) more ice than for the same day in 2007 and 1.36 million square kilometers (523,000 square miles) below the 1979 to 2000 average. Ice extent on July 21, 2009 remained 8.06% higher than the same day in 2007, yet was 2.44% below the same day in 2008 and 14.06% below the 1979-2000 average for that day.

Figure 2. The graph above shows daily sea ice extent as of July 21, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; the purple line shows 2008; and the solid gray line indicates average extent from 1979 to 2000. Sea Ice Index data.—Credit: National Snow and Ice Data Center
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Conditions in context

During the first two weeks of July (July 1 to 16), Arctic sea ice extent declined at an average rate of 97,000 square kilometers (37,000 square miles) per day. This decline was faster than in 2008, when it was 87,000 square kilometers (34,000 square miles) per day, but slower than in 2007, when ice extent declined at a rate of 111,000 square kilometers (43,000 square miles) per day .

Figure 3. In recent years, sea ice melt in the Arctic Ocean has begun earlier than in the past. Colors in the map above indicate the date of melt onset; gray regions indicate areas where data is not available or not retrievable. Variations in ice type may result in some errors. Data are from the Defense Meteorological Satellite Program (DMSP) F-series satellite SSM/I and SSMIS sensors. —Credit: National Snow and Ice Data Center: Algorithm provided by Thorsten Markus, Goddard Space Flight Center
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Early melt onset

Early or extended melt in response to rising atmospheric temperatures appears to be one of the factors contributing to the sharp decline of summer Arctic sea ice extent. When ice melts earlier, it leads to a lower albedo surface that absorbs more of the sun’s energy and promotes further melt.

The same satellite instruments that are used to measure ice extent also provide information on when ice begins to melt each year. In recent years, Arctic sea ice melt onset has begun earlier than in the past, and 2009 continues this pattern. Compared to average conditions over the period 1979 to 2000, melt this year started a week early in the Beaufort, Chukchi and Kara seas. In some regions such as the East Greenland and the Barents seas, melt began more than two weeks earlier than usual.

Figure 4. Scientists who contributed to the July Sea Ice Outlook report expect another low Arctic sea ice extent in September. Most of their projections fall near or between the 2007 record low and the second-lowest extent, which occurred in 2008.—Credit: From National Snow and Ice Data Center, courtesy SEARCH Sea Ice Outlook.
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Outlook for September

As interest in Arctic sea ice builds, national and international scientific organizations are working together to make projections of the September 2009 sea ice minimum. Their assessments are summarized in the Study of Environmental Arctic Change Sea Ice Outlook.

The researchers make projections using a variety of techniques, ranging from sophisticated sea ice models to simpler statistical analyses. Their most recent report points to another extreme September sea ice minimum in 2009, with projections for the September monthly average ranging from 4.0 to 5.2 million square kilometers (1.5 to 2.0 million square miles). However, sea ice forecasting efforts are still in their infancy, and the resulting projections should not be taken as a true forecast, but rather as a way to gain insights into the changing Arctic climate. Whether or not 2009 will break the 2007 record still depends largely on atmospheric conditions during the rest of the summer.

Figure 2. The graph above shows daily sea ice extent as of July 6, 2009. The solid blue line indicates 2009; the dashed green line shows 2007; and the solid gray line indicates average extent from 1979 to 2000. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.—Credit: National Snow and Ice Data Center
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Conditions in context

Through most of June, ice extent tracked close to two standard deviations below the long-term mean and just above the levels observed in 2007. By the end of June 2009, ice extent was 337,000 square kilometers (130,000 square miles) higher than extent at the end of June 2007.

During June, the Arctic Ocean lost a total of 2.05 million square kilometers (792,000 square miles) of ice, an average decline of 68,300 square kilometers (26,400 square miles) per day.

Figure 3. Monthly June ice extent for 1979 to 2009 shows a decline of 3.3% per decade. —Credit: National Snow and Ice Data Center
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June 2009 compared to past Junes

Compared to previous Junes, ice extent in June 2009 was extremely close to the last two years, falling within 30,000 square kilometers (12,000 square miles) of the June extent in 2007 and 2008. The long-term trend indicates a decline of 3.3% per decade, an average of 40,100 square kilometers (15,500 square miles) of ice per year.

Figure 4. The map of sea ice concentration from AMSR-E from July 5, 2009 shows low ice concentrations in the Laptev Sea, where atmospheric temperatures have been particularly warm in the month of June. NASA AMSR-E data.—Credit: From National Snow and Ice Data Center courtesy IUP, University of Bremen, Germany
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Warm conditions speed regional melt

In June, the Arctic saw warm temperatures over the Laptev Sea and the northern Beaufort Sea, while the Atlantic sector of the Arctic was slightly cooler than normal. The warm temperatures in the Laptev Sea corresponded to quickly declining ice concentrations in the area. The decline can be seen in sea ice concentration analyses produced at the University of Bremen using NASA Advanced Microwave Sounding Radiometer-Earth Observing System (AMSR-E) data. We expect this region to become largely ice-free in the next few weeks.

Figure 5. The map of sea level pressure (in millibars) from June 1 to 30, 2009 shows high pressure (red) over the northern Beaufort Sea and a weak low (purple) centered over Novaya Zemlya. —Credit: From National Snow and Ice Data Center courtesy NOAA/ESRL Physical Sciences Division
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Southerly winds promote warmth

The warmth in the Laptev Sea is consistent with a pattern of southerly winds in these areas, which can be linked to the area of low atmospheric pressure centered just north of Novaya Zemlya Island. Note also the strong high-pressure cell (an anticyclone) over the northern Beaufort Sea.

This contrast between high and low pressure is broadly similar to the atmospheric circulation pattern that set up in 2007. In 2007, that pattern contributed to a significantly accelerated decline in ice extent during July, and a record minimum low in September. Will the same acceleration in ice melt occur this year? If so, a new record low minimum extent becomes more likely. So far, an acceleration has not been observed. As July progresses, the Arctic sun gets lower on the horizon, incoming solar energy decreases, and the chances of such a rapid decline become less likely.

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