Planet Earth Weekly

Climate Change and Renewable Energy: Saving Our Planet for Future Generations

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The Arctic Basin: Warming Faster than the Planet in its Entirety

Arctic Ocean

Melting of the Arctic Sea Ice

“The arctic basin is warming faster than most of the earth’s surface.”

By Dr. John J. Hidore
June 8, 2018—–The Arctic Basin consists of the Arctic Sea and the surrounding land. The climate of the basin is warming faster than any other area of Earth’s surface. Air temperature over the arctic has increased an average of nearly three degrees Celsius (five degrees Fahrenheit) over the last century. This is almost double that of the global average.

The Energy Exchange in Change of State Between Ice and Water

One very important feature of the energy balance distinguishes the Arctic Basin. Over 95% of the earth’s surface, the major change in the state of water in the environment is between liquid and gas. This entails evaporation and condensation. In the Arctic it is between solid and liquid. There is an energy exchange of about 80 calories per gram between solid and liquid. For the rest of the earth the energy exchange is much higher. The energy exchange between liquid and gas is 590 calories per gram. This is nearly seven times that of ice and water.

The implication of this is that melting or freezing takes place with relative small changes in heat added or heat lost in the environment!

The energy exchange in melting artic

Melting of the Arctic

Energy Exchange in the Tundra

Surrounding the Arctic sea is a grassland, generally known as the tundra. Such a grassland is found primarily only in the Northern Hemisphere. The southern margin of the tundra is delimited by the polar margin of a coniferous forest. Specific regions that contain tundra are the northern coast of North America, Iceland, Spitsbergen, coastal Greenland, and the Arctic borderlands of Eurasia.

A significant feature of the tundra is permafrost. Permafrost is permanently frozen ground. Extensive area of land in the basin are covered with it. Permafrost can vary from centimeters to many meters thick.

Ice and snow are highly reflective of solar radiation. However, in the summer months some of the solar radiation melts the permafrost. The surface layer of permafrost thaws leaving the deeper layer frozen. The result is that lakes and ponds are a characteristic of the tundra. Once the permafrost melts at the surface, the wet ground absorbs much more radiation and the thawing increases. However, except on the margins of the permafrost, there remains frozen ground beneath the surface.

How deep the permafrost melts will vary. The point is that once the surface thaws the solar energy that is absorbed goes up substantially. This in turn increases the rate of the thawing of the permafrost. As the earth’s atmosphere slowly warms this process is being accelerated.

climate change

The exchange of energy is causing rapid arctic melting.

Energy Exchange in the Arctic Sea

The Arctic Sea is a part of the world ocean that is frozen much of the year but increasingly is open during the summer months. The season when melting occurs has increased by three weeks since records began. At present, even in the summer, there is a large area that remains frozen. As the atmosphere slowly warms more of the ice cover melts. Open water absorbs much more radiation than the ice and this increases the temperature of the water which then increases melting of the ice. As a result, over recent decades, the sea ice has been thinning or melting entirely over large areas. Just as on land the conversion from sea ice to open water is increasing at an increasing rate.

Climate change

The rapidly melting artic

In summary, the arctic basin is warming faster than most of the earth’s surface. Part of the explanation lies in the fact that the amount of energy it takes to change the state of water between solid and liquid is much less than it takes to change the state between liquid to gas. There is thus a net gain in heat that is proportionately higher than that of the rest of the planet. As the summer season increases in length more heat is absorbed in the environment adding to the general global warming!

Warming of the Arctic


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Montreal Protocal Is Making a Difference

Montreal Protocol

With and Without Montreal Protocol

Scientists around the world soon realized the amount of damage the chlorofluorocarbons were doing to the environment.

By Dr. John J. Hidore

August 17, 2016—-Ultraviolet radiation is high intensity energy that Earth receives from the Sun. Ozone (O-3), high in the stratosphere, filters out much of this ultraviolet radiation. Part of this high-energy portion of the ultraviolet radiation spectrum is known as ultraviolet-B (UVB). Although the atmosphere blocks most UVB radiation, it does not block all of it. This UVB radiation is very harmful to living organisms.

Any reduction in atmospheric ozone lets more ultraviolet radiation through the atmosphere to reach the surface. Plants did not flourish on Earth until there was enough atmosphere and ozone to block much of the UVB radiation. All plants and animals now existing and living in sunlight have adapted to ultraviolet radiation in some manner. However, they vary widely in their tolerance of UVB. Plants that developed in climates with high-intensity sunlight show a variety of defense mechanisms for UVB. Some produce pigments that absorb UVB radiation.

In arid climates, plants develop thick, shiny leaves. Cacti and olive trees are examples. Most living organisms are subject to damage if UVB radiation increases. Since plants cannot adjust their behavior to changing solar radiation they are vulnerable to increases in UVB radiation. Animals have also adapted to UVB radiation. Nearly 90 percent of marine species living in the surface water surrounding the Antarctic Continent produce some form of chemical sunscreen.

Ozone Depletion

Size of Ozone Depletion

Ultraviolet-B and Human Health

Humans have adapted to UVB radiation by manufacturing melanin in the skin. This is a pigment that blocks ultraviolet radiation. A summer tan results from increased production of melanin. Persons with very fair skin do not readily manufacture melanin and sunburn very easily. Over exposure to ultraviolet radiation results in aged skin, skin cancer, and a weakened immune system. The risk of skin cancer is much greater from overexposure by a sunburn than from steady low doses. A single blistering sunburn in a person 20 to 30 years of age triples the risk of skin cancer.

The risk of getting skin cancer can be reduced with reasonable care. The first rule is to avoid exposure to the midday sun. The most dangerous hours are between 10 A.M. and 2 P.M. There is an old saying: “Only mad dogs and Englishmen go out in the noonday sun.” If exposure to the sun is necessary, using a sunscreen with a rating of 15, based on Ultraviolet-B radiation, helps reduce skin damage.




In 1974, scientists warned there was evidence to suggest that compounds known as chlorofluorocarbons (CFCs) were having a depleting effect on stratospheric ozone layers. These compounds are not natural compounds.

First synthesized in 1928, these compounds promised to have many uses. They are odorless, nonflammable, nontoxic, and chemically inert. They first came into use in refrigerators in the 1930’s. Since World War II, CFCs have been used as propellants in deodorants and hair sprays, in producing plastic foams, and in cleaning electronic parts. They do not react with most products dispersed in spray cans. They are transparent to sunlight in the visible range. They are insoluble in water and are inert to chemical reaction in the lower atmosphere. For these reasons they are valuable compounds.

Antarctic Ozone Hole

Chlorofluorocarbons rise into the upper atmosphere where they break apart under ultraviolet radiation. This breakdown releases chlorine, which interacts with oxygen atoms to reduce the ozone concentration. The most disturbing reduction in atmospheric ozone is that found over the Antarctic Continent and is referred to as the ozone hole.

The ozone hole over Antarctica has occurred in September and October since the late 1970’s. During the Antarctic spring, there is a decrease in ozone north from the pole to nearly 45° south latitude. In August and September 1987, the amount of ozone over the Antarctic reached the lowest level recorded to this date. In the fall the ozone hole covered nearly half of the Antarctic Continent.

The same process takes place elsewhere in the atmosphere, but at higher altitudes and at slower rates. Ozone depletion is less outside the Antarctic, where the difference is significant. There is no Arctic ozone hole like that of the Antarctic. Temperatures are warmer, and there is more variable weather in the Arctic which provide less favorable conditions for the necessary chemical and circulation processes. Ozone depletion contributes to global warming. The additional ultraviolet radiation reaching the earth’s surface adds heat to the lower atmosphere.

International Cooperation has Made a Difference

Scientists around the world soon realized the amount of damage the chlorofluorocarbons were doing to the environment. The U.N. Environment Program called a conference in Montreal, Canada, in September 1987, that drafted a treaty restricting the production of CFC’s. The agreement is officially termed the Montreal Protocol.

International support for the treaty led to a substantial reduction in CFC production. The reduction in CFC’s has led to a decline in the amount of UV radiation getting through the upper atmosphere. The average size peaked in the 1990’s. Evidence now indicates that the average extent of the Antarctic ozone hole is declining. In the Antarctic spring of 2015, (September and October) the extent of the hole was only about ½ of what the previous maximum area had been. Hopefully, the size of the hole will continue to decline. NASA has indicated that it might be gone by 2050. This accord shows that international cooperation can occur with respect the environmental problems.

The Paris Conference on climate change can make a huge difference to global warming and climate change if the signatories follow through on their commitments.

The Paris Conference on Climate Change

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Global Changes of Note in the Early 21st Century

Climate Change

The earth’s overall temperatures are increasing every year.

Greenhouse gases let solar radiation through the atmosphere, but trap outgoing earth radiation

By Dr. John J. Hidore

October 18,2014—Planet Earth is now in a period of rapid change. The first years of the 21st century serve to indicate how fast it is changing. A fundamental driving force in many of these recent changes is the growth of the human population. From the time of its origin until now the population has been growing faster and faster. It took modern humans some 200,000 years to reach a total of one billion individuals. We have added another billion in less than 15 years since the start of the century.

A major element in change is now global warming and its associated changes. The warming is largely due to the accumulation of greenhouse gasses in the atmosphere. Greenhouse gases let solar radiation through the atmosphere, but trap outgoing earth radiation. Heat thus accumulates in the earth system.

Carbon Dioxide and Methane

The major greenhouse gases are carbon dioxide and methane. Both of these gases have been accumulating for the last several centuries. Since the start of the industrial revolution, the burning of organic fuels has released more than 500 billion tons of carbon dioxide into the atmosphere. The concentration in the atmosphere is now the highest it has been in the past 800,000 years. The gases are at their highest levels in historic times and have now passed 400 parts per million.

Four countries contribute most of the carbon dioxide. They are China, India, The United States, and Russia. In the past year, each of these countries increased their emissions of carbon dioxide. The United States, which had been stabilizing emissions, increased its contributions. At a recent conference on climate change and greenhouse gas emissions, China, India, and Russia did not attend. Globally an estimated 39.8 billion English tons (36.1 billion metric tons) of carbon dioxide were contributed to the atmosphere in the last year. That is 2.3 % more than the previous year. Almost all carbon dioxide comes from burning fossil fuels. .

Methane levels are also at record levels. It forms in the natural world largely from the decomposition of organic matter. It has begun to accumulate during the past two centuries. Since 1750, the level of methane in our atmosphere has more than doubled, from about 700 to 1800 parts per billion (ppb) in 2013. The current level is the highest in at least the last 650,000 years. About half of the increase has occurred since 1960. Methane comes from a variety of sources including agriculture, mining, and manufacturing, and fracking

Increasing Greenhouse Gases

Global temperatures have increased accompanying the increase in greenhouse gasses. In the months of May and June of this year (2014) the highest average global atmospheric temperatures, since records began, were recorded. In 2012, worldwide land-surface temperatures for the months of June through August were the hottest ever. Australia recorded its warmest year of record in 2013. Not all of the planet experienced unusually warm conditions at this time, but overall, earth’s temperature has increased.

Walruses need Sea ice

Walruses Cling to Melting Sea Ice.

Parts of the arctic region are now the warmest they has been in 44,000 years. The warming is taking place around the North Pole including the Arctic Ocean and the surrounding land masses. Most of the ice shelves in the Canadian Arctic broke away from land during the past 14 years. Every summer, for the last ten years, the area of sea ice has been below the average of the previous 20 years. Sea ice in the Arctic sea reached is lowest level ever on September 16, 2012.

2012: Records Broken in the U.S.

2003-2012 The warmest decade ever recorded in the United States.
2011-2012 The winter (Dec, Jan, Feb) was the fourth warmest since records began in the 1890s. It was about four degrees Fahrenheit above the average and the warmest since the year 2000. Twenty seven states had one of the 10 warmest of record.
2011-2012 Warmest records in U.S. History.
2012 Warmest year ever recorded in the United States. The year averaged 3.2F above the average of the 20th century.
2012 March sets record high temperatures. More than 7700 U.S daily-high temperature records were set.
2012 In March more than 90 cities set record highs for the month.
2012 The six warmest 12 month periods so far in the U.S. ran through 2012.
2012 Global land surface temperatures in the months from June to August were the warmest ever.
2012 September tied for the warmest ever in the United States,
2011-2012 The 12 months from August 2011 to July 2012 were the warmest ever in the United States.
2012 In July of this year all 50 states in the Unites States set record highs. During the summer of 2012, ninety degree temperatures forced the Tennessee Valley Authority to shut down three nuclear power reactors.
2012 Drought affected as much as 65% of the lower 48 states.

In 2012 eleven extreme weather and climate events each cost the U.S. at least one billion dollars!


Arctic Methane Adds to Global Warming

Methane Leaking through the Cracks

(Photo credit: NASA)   Melting of   permafrost is releasing trapped methane into the atmosphere.

By John J. Hidore

Melting of  the Permafrost  

 December 7, 2013–A characteristic of much of the land surrounding the Arctic Sea is a phenomenon known as permafrost. Permafrost is ground which is frozen in winter. In summer the ground surface melts, but does not melt down far enough to thaw the frozen soil all the way to the bottom. Along the southern boundary of the permafrost, the temperatures within the soil are close to the freeze-thaw temperature. Only a slight increase in temperature can melt permafrost over large areas. Along this boundary, the permafrost is melting downward at a rate of about three feet (1 meter) every ten years. Around the base of Mt. McKinley large areas of arctic meadow have turned into a mix of ponds containing water-loving plants and dry meadows. Much of the melting of the permafrost has taken place in the past several decades. Permafrost is not restricted to North America. Somewhere between 20 and 25% of Earth’s land area contains permafrost. In China, the permafrost is estimated to be melting northward at the rate of about 1.6 km (1 mi) every year. Around the Arctic Sea the permafrost is now completely melting in summer on the southern margins.

Methane (CH4) is a greenhouse gas found in small amounts in the atmosphere under natural conditions. It is a gaseous hydrocarbon that is clear, odorless and flammable. It forms in the natural world largely from the decomposition of organic matter. It has begun to accumulate during the past two centuries. Since 1750, the level of methane has more than doubled from about 700 to 1800 parts per billion (ppb) in 2013. The current level is the highest in at least the last 650,000 years. About half of the increase has occurred since 1960. The additional methane comes from a variety of sources including agriculture, mining, and manufacturing.
Historic Changes in Atmospheric Methane
Date Parts per Billion
By Volume
100,000 YBP 500
70,000 YBP 650
20,000 YBP 350
1750 700
19th Century 800
1990s 1600
2013 1800 ___________________

Methane: Seeps and Fountains

Permafrost provides a barrier for gases trapped beneath the frozen soil and ice. A large amount of methane is trapped beneath permafrost and ice covered lakes, perhaps trillions of tons. Some of the methane has been trapped under the ice for hundreds of thousands of years. Rapid melting of the permafrost is releasing trapped methane into the atmosphere. The melting of sea ice and decomposition of vegetation at the bottom of ponds and lakes contributes to the methane emissions. Ice capped seeps are mainly found along the boundary of the permafrost. They are also found around the retreating margins of glaciers. Scientists have recently documented 150,000 methane seeps in Alaska and Greenland. In Russia more than 100 methane fountains have been found, some more than one-half mile wide. These fountains send methane directly into the atmosphere. On a global basis, methane is now second to carbon dioxide in volume of emissions. It accounts for about 23 % of greenhouse gases. The combination of CO2 and methane combined account for 93% of greenhouse gas emissions at present.

Water vapor normally is not present in any significant amounts above the troposphere. Methane rises in the atmosphere, passing through the troposphere to the stratosphere. In the stratosphere the sun breaks down methane and hydrogen oxidizes to form molecules of water vapor and ice crystals. The accumulation of water vapor and ice particles forms thin clouds. These clouds reflect Earth radiation back to the surface, compounding global warming. Computer models show that a doubling of methane into the atmosphere could increase water vapor in the stratosphere by approximately 30%.

Perpetuation of Global Warming 

Because global warming is most rapid in sub-Arctic regions, rapid melting of the permafrost is taking place and increasingly releases methane into the atmosphere. The release of methane in sub-polar regions is self perpetuating. If more methane is released into the atmosphere, it will lead to still more warming and more methane release. If only one percent of the methane known to be buried in the ground were emitted to the atmosphere, it would have double the warming effect of all greenhouse gases placed into the atmosphere to date.

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Greenland: Mining of Uranium and Rare Earth Metals


Greenland: The long term effects of mining in Greenland could be devastating to the environment and the economy.(Photo credit: Beechwood Photography)

Uranium waste from mining contains radioactive decay products which have the potential to effect surface, ground water, soil, and air quality in Greenland for thousands of years.

By Lin Smith

Greenland’s Ice Sheet
November 1o, 2013—Greenland is a semi-autonomous part of the Kingdom of Denmark. It is located between the Arctic and Atlantic Oceans. Greenland’s ice sheet is approximately 660,000 sq. miles, which is about 80% of its surface, second only to the Antarctic Ice Sheet. Its thickness averages more than one mile. The current ice sheet in Greenland is approximately 110,000 years old and there has been a continuous ice sheet for over 18 million years. Greenland’s ice sheet contains valuable records and, according to Wikipedia, the data collected from the ice sheet is “greater than in any other natural recorder of the climate, such as tree rings or sediment layers.” But according to the satellite monitoring this ice sheet since the 1970’s, it has been steadily growing thinner. As stated in last week’s post by John J. Hidore, “As a result of the warmer temperatures, the ice has been thawing further from shore and the remaining perennial ice pack has been getting thinner. In some areas it is only half as thick as it was a few decades ago.” This melting of the ice sheet allows for passage of freighters, without ice breaker ships, to places that were previously inaccessible.

Reducing Dependency on Denmark
Currently, more than half of Greenland’s revenues come from Denmark, but Greenland’s goal is to reduce dependency on Denmark’s subsidies. Greenland’s government has recently voted to allow mining of uranium, which has had a 25 year ban. Uranium is often found mixed with rare earth metals, therefore, requiring the  ban to be lifted on both rare earths metals and uranium. Also, there is a growing demand for rare earth metals, as they are used in many every day devices such as cell phones, rechargeable batteries, DVDs, computers, and fluorescent lighting. Greenland’s government approved the end of the uranium ban recently in a 15 to 14 vote, arguing with Denmark that “its autonomy from Denmark will let Greenland export uranium.”  Denmark has said Greenland can decide only on excavation of uranium, not on its exportation. Greenland Minerals, according to the Wall Street Journal, is “developing an $810 million rare-earths and uranium project that it hopes will produce enough uranium and zinc to subsidize mining rare earth metals at a lower cost than in China, the world’s largest producer.”

Environmental Effects of Mining
China is currently the world supplier of rare earths but in 2013 China put a cap on the production of rare earths stating that overmining has created massive damage to their environment and China “no longer wants to pay the environmental costs of supplying the vast bulk of the world’s rare earths,” as reported by David Stanway. There has been little or no regulation of the mining of rare earth metals in China, leading to many environmental disasters. For example, in Northern China near the Mongolian border radioactive water from a mine is leaking into the Yellow River, which is a major source of drinking water and in south-central China, there are a large number of illegal rare earth strip mines. In southeast China, runoff from rare earth mines are destroying rice fields and water sources.

With the mining of uranium comes radioactive decay products, which, as with the rare earth metals, have the potential to affect the quality of surface and ground water, soil, and air. Tailings from mining uranium can contaminate a site for thousands of years according the article, “Potential Environmental Effects of Uranium Mining, Processing, and Reclamation” published by the National Academies Press. This article also states that “limited data exists to confirm the long-term effectiveness of uranium tailings’ management facilities that have been designed and constructed according to our modern best practices.”

Long Term Effects of Uranium 
Forty-eight NGOs (nongovernment organizations), including Greenpeace, have signed a petition to stop mining in Greenland. The reasons they have listed include: 1.There will be chemical pollution from radioactive tailings. 2.There is no safe technology to store radioactive residues. 3.The Arctic environment is vulnerable to pollution, as it is extremely slow to recover due to the cold temperatures which slow down the chemical breakdown of the contaminants. 4.Up to 85% of the radioactivity from uranium mining will remain in the tailings and leakage is highly possible, spreading the radioactive materials throughout the pristine environment. 5. As in the mining of rare earth metals in China, leakage of radiation may accumulate in the food chain, thus contaminating fish and causing genetic damage to life in the Arctic. 6. Contamination could eliminate the fishing industry of Greenland.

Greenland Minerals and Energy LTD is licensed to mine in Greenland and according to the NGO organizations, “Greenland Minerals does not have sufficient economic resources to clean up ecological damage done to the region from the millions of tons of radioactive waste, nor does Greenland itself have the resources to restore the damage.”

And finally,  responsible nations and citizens of the world need to ask themselves, “What would be the long term cost of opening Greenland to the mining of uranium and rare earth metals?” The NGO organizations summarize it well, “The long term economic damage could far exceed any compensation from jobs or short term economic success!”

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Arctic warming and Sea Ice

By John J. Hidore

SHEBA (Surface Heat Budget of the Arctic Ocean...

Researchers taking data in a melted area of the Arctic Ocean ice pack. (Photo credit: Wikipedia)

Early forecasting of Arctic warming suggested a possible ice free path through the North West Passage in the summer months perhaps between 2050 and 2100. 

The Arctic: Rapid Changes in Temperature

November 1, 2013—Earth’s two polar regions of the Antarctic and Arctic differ a great deal. The Antarctic is a land mass surrounded by sea. In contrast to the Antarctic, the Arctic region is essentially a sea surrounded by land. This difference results in substantially different climatic conditions. Today the most rapid changes in temperature and climate are taking place in the sub-arctic regions of the northern hemisphere.

Extending over the North Pole and for varying distances southward is the Arctic Sea. In the winter months the sea is covered with a broken sheet of floating ice, up to perhaps 13 feet (4 meters) thick. Sea ice is defined as sea surface on which at least 15% of the surface is covered with ice. This ice is generally thickest in the middle of the sea and thins toward the surrounding land. Winter sea ice reaches the Arctic shoreline or very near it. However, even in winter there is always some open water. There are open cracks in the ice as the rotation of the earth causes stress in the ice. These cracks continually open and refreeze. When the sea is covered with snow and ice the bright surface absorbs only about 20% of the solar radiation. The rest is reflected back to space. This reflected sunlight does not alter the frozen surface.

Long Days And Intense Sunlight

In summer, the ice melts away from the shores of the continents and islands. The ice is thinner on the edges and so it thaws more readily. Around the summer solstice, in late June, the sun is highest in the sky and the days are the longest in the northern hemisphere. The long days and intense sunlight are a primary factor in the melting. The effect of the sun on open water is very different from that of sun on snow and ice. When the surface is open water, the water absorbs up to 90% of the radiation. This absorbed solar radiation warms the water. Away from shore there is sea ice which does not melt in the summer. This is thicker than ice near land masses.

The Receding Arctic Ice Pack

Satellite images of the Arctic ice have been available since the 1970s. The satellite data confirms that sea ice has declined throughout the Arctic Basin, but it has receded more in some places than others. At times, in recent years, the air temperatures over the arctic have been more than 10ºF (5.5 ºC) warmer than the average for the last 30 years. As a result of the warmer temperatures, the ice has been thawing further from shore and the remaining perennial ice pack has been getting thinner. In some areas it is only half as thick as it was a few decades ago. The present area of sea ice is about 50,000 mi2. (125,000km2). The ice pack has been melting faster in summer since the beginning of the twentieth century. The summer melting of sea ice has been taking place at an ever increasing rate. It is now taking place much faster than predictions made a decade ago. The additional heat absorbed by the Arctic Ocean contributes to global warming. The heat absorbed by the water in summer eventually escapes to the atmosphere in the fall and winter, as the water cools and freezes. The heat transferred from open water is 100 times greater than from ice.

Forecasting Arctic Warming

Early forecasting of Arctic warming had suggested a possible ice free path through the North West Passage in the summer months,  perhaps between 2050 and 2100. However, to the astonishment of nearly everyone, at the end of the summer melt period in 2007, there was an open passage of water circling the Arctic Sea. It was hailed as the opening of the Northwest Passage from Atlantic to the Pacific.

Every summer for the past decade the area of sea ice has been below the average of the previous 20 years. In the summer of 2011 sixteen ships made the trip through the Northwest Passage. None of these required the use of an ice breaker ship. On September 16, 2012, Arctic sea ice reached the lowest since data has been available. In September 2013, a coal carrying freighter sailed through the Northwest Passage, also without the aid of an ice breaker. Whether the passage remains open in future years remains to be seen. On September 13, 2013, the area of sea ice reached its minimum for the summer. However, the area of sea ice actually expanded some 40% from the previous year. The additional ice had formed around the outside of the ice pack and was quite thin

The evidence of change in sea ice parallels other evidence that global warming is taking place much faster than past climate models have forecasted. At its current rate of melting, the Arctic Ocean could be totally ice free during the summers within the next decade. An ice free arctic will substantially alter the climate of the northern hemisphere sub-polar regions.

Sources of sea ice data Of Change/sea ice