Why does the melting of arctic sea ice matter?

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.


The Arctic

Dispatches from the Front Lines of Climate Change

By definition, global climate change is reflected in a host of changes all over the planet. But changes do not occur uniformly across the globe. Changes in the Arctic have been generally more rapid than those anywhere else on Earth. Strange sights — such as forests of “drunken trees” loosened by thawing permafrost — provide dramatic visual evidence of this rapid change (Figure 1).

Why is Earth Warming?

Greenhouse gases such as carbon dioxide and methane absorb heat emitted from Earth’s surface. Increases in the atmospheric concentrations of these gases cause Earth to warm by trapping more of this heat.

Human activities — especially the burning of fossil fuels — have increased atmospheric carbon dioxide concentrations by about 40 percent, with more than half the increase occurring since 1970.

Since 1900, the global average surface temperature has increased by about 0.8°C (1.4°F).

Why Does the Melting of Arctic Sea Ice Matter?

FIGURE 1. This forest of “drunken trees” in Alaska is a clear sign of thawing permafrost. When permafrost thaws it can make the ground buckle, causing trees to lose their footing and tip over at odd angles. Source: National Snow and Ice Data Center, University of Colorado, Boulder/Tingjun Zhang

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.


Arctic Ocean Acidification

As well as warming the atmosphere, excess carbon dioxide is also absorbed by the ocean, forming carbonic acid that makes seawater more acidic (lower pH), a phenomenon called ocean acidification.

Ocean acidification threatens the health of marine organisms, such as corals and some shellfish, which have shells composed of calcium carbonate — a material that dissolves at lower pH.

As the pH of sea water decreases, it will become more difficult for these organisms to form or maintain their shells, with impacts that ripple throughout the marine ecosystem.

The Arctic Ocean is particularly sensitive to ocean acidification: frigid Arctic waters absorb more carbon dioxide than temperate waters. Additionally, declines in the extent of summer sea ice will expose more ocean area, allowing for greater transfer of carbon dioxide from the atmosphere into the ocean.

Why Does the Melting of Arctic Sea Ice Matter?

Tiny sea snails called pteropods are one example of an Arctic marine species at risk from ocean acidification. Pteropods swim near the ocean surface and provide food for a variety of fish. Healthy pteropods have smooth, transparent shells (top). In lower pH conditions, pteropod shells can start to dissolve and appear cloudy, ragged, and pockmarked (bottom). Source: NOAA


Temperatures are rising twice as fast in the Arctic as compared to the average global temperature rise (Figure 2). The most dramatic manifestation of this warming is seen during the Arctic winters, which are becoming milder.

The temperature of the Arctic Ocean is also increasing, a pattern that is exacerbated as sea ice melts, leaving more of the water’s surface exposed and allowing more heat to be taken up by the open water during the summer months.

Why Does the Melting of Arctic Sea Ice Matter?

FIGURE 2. Temperatures have risen faster in the Arctic than elsewhere on the globe. This map depicts the temperature trend from 1950 to 2014.

This analysis was assembled using publicly available data from roughly 6,300 meteorological stations around the world; ship-based and satellite observations of sea surface temperature; and Antarctic research station measurements.

Source: NASA Earth Observatory/ NASA Goddard Institute for Space Studies (GISS)/ Kevin Ward

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.



If you were to stand at the North Pole, the snow and ice under your boots would feel rock-solid, and its white expanse might extend as far as you could see. But you would not be standing on land, because Earth’s North Pole is in the middle of the Arctic Ocean. You would be standing on sea ice — ice floating on the ocean’s surface.

Each summer, as temperatures rise above freezing, the ice begins to melt and the area covered by sea ice shrinks (Figure 3). In winter, sea ice coverage expands again as sea water freezes.

But over the past several decades, warmer temperatures have meant there is less sea ice left at the end of the summer. Using satellites, scientists have found that the area of sea ice coverage each September has declined by more than 40 percent since the late 1970s, a trend that has accelerated since 2007.

In fact, by the end of each of the eight summers from 2007–2014, Arctic sea ice extended over less area than at any time in the preceding three decades — the time period for which we have satellite observations. In 2012, the ice shrank to its smallest extent ever recorded by satellites, with the ice covering only half the area covered just 30 years earlier.

This striking decrease in summer ice has also caused winter ice to become thinner and less stable.

Even a few decades ago, a large core of sea ice survived the summer and beyond, thickening and hardening over many winters to become multiyear ice (generally 3–4 meters [10–13 feet] thick).

But now, more summer melting means an increasing fraction of winter sea ice cover is first-year sea ice (generally only 1–2 meters [3–7 feet] thick) that melts more quickly and breaks up more easily in the summer, contributing to the overall trend of sea ice loss (Figure 4).

Why Does the Melting of Arctic Sea Ice Matter?


These images of Alaska’s Bristol Bay, taken by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the NASA Aqua satellite, illustrate the thinning and thawing of arctic sea ice each spring.

The image on the left was taken on April 11 2012, and shows sea ice hugging the shore. Two weeks later, on April 24, the ice had retreated (right). Source: NASA Earth Observatory/ Jesse Allen

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.


Why Does the Melting of Arctic Sea Ice Matter?

FIGURE 4. The extent of multi-year ice is decreasing rapidly. These visualizations show sea ice coverage in 1980 (left) and 2012 (right). Multi-year ice is shown in bright white, while younger sea ice is shown in light blue to milky white. The data show the ice cover for the period of November 1 through January 31 in their respective years. Source: NASA Earth Observatory

The Science of Predicting Sea Ice

Accurate sea ice predictions are crucial to modeling atmospheric and oceanographic processes, understanding ecological changes, and helping people know what to expect when venturing into the area to extract resources or transport goods.

Scientists use satellites, ships, and airplanes to measure the areal extent of ice covering the Arctic Ocean, the thickness of the ice, and other characteristics.

These measurements are then integrated with computer models to project what could happen in the future.

Despite sophisticated measurements and computer models, our prediction capability is limited. For example, seasonal forecasts from 21 research groups all underestimated the record-setting summer sea ice loss of 2012. The 2012 National Research Council report Seasonal-to-Decadal Predictions of Arctic Sea Ice: Challenges and Strategies offers strategies to improve sea ice projections.

Why Does the Melting of Arctic Sea Ice Matter?

The blanket of ice coating Earth’s northernmost seas is thin and ragged by summer. This photo shows scientists treading carefully over ice in the Canada Basin of the Arctic in July 2005.Source: NOAA/OAR/OER/Jeremy Potter

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.



Ice is melting at a rapid pace on the land masses that encircle the Arctic Ocean.

Glaciers, many of which have endured since the last Ice Age or longer, are becoming smaller (Figure 5). Those that border bodies of water are increasingly breaking off into icebergs, a process called calving. The icebergs then float away and gradually melt into the sea.

The Greenland ice sheet is essentially an enormous glacier that extends about 1,699,000 square kilometers (656,000 square miles) and covers most of the island of Greenland. In recent decades, this ice sheet has begun to decrease in size and mass as a result of warmer summer temperatures melting ice at the surface, and increased calving of ice at the island’s edges.

Snow cover has also decreased as temperatures rise and snow melts off more quickly in the spring and summer. For example, snow cover in June 2012 was 40 percent below the average from 1971–2000 — the baseline period of observations — in many areas of the Arctic.

This loss of ice from Arctic land masses contributes to sea level rise, alters the way water moves over and through the land, and could affect the circulation of the oceans and atmosphere globally.

Why Does the Melting of Arctic Sea Ice Matter?

FIGURE 5. Recent losses of land ice are illustrated by comparing a 1976 photograph of Muir Glacier in Glacier Bay National Park and Preserve, Alaska (left) with a 2003 photograph of the same glacier (right).

The 1976 photograph shows the calving edge of Muir Glacier (where icebergs break off) extending the width of the fiord, and aside from algae growing on a lighter colored dike, there is no vegetation visible in the photograph.

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The 2003 photograph documents the disappearance of Muir Glacier from the field of view, and shows vegetation beginning to develop. Source: USGS/Bruce F. Molnia.

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Suggested Citation:“The Arctic.” National Research Council. 2015. Arctic Matters: The Global Connection to Changes in the Arctic. Washington, DC: The National Academies Press. doi: 10.17226/21717.


Snow largely a no-show for 2014 Iditarod Trail Sled Dog Race

Quick Facts on Arctic Sea Ice | National Snow and Ice Data Center

Why Does the Melting of Arctic Sea Ice Matter?

Sea ice can take on a variety of textures. When waves buffet the freezing ocean surface, characteristic “pancake” sea ice forms. This sea ice was photographed near Antarctica. Credit: Ted Scambos, NSIDC

Sea ice is frozen ocean water. It forms, grows, and melts in the ocean. In contrast, icebergs, glaciers, and ice shelves float in the ocean but originate on land. For most of the year, sea ice is typically covered with snow.

Why is Arctic sea ice important?

Arctic sea ice keeps the polar regions cool and helps moderate global climate. Sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space.

As sea ice melts in the summer, it exposes the dark ocean surface. Instead of reflecting 80 percent of the sunlight, the ocean absorbs 90 percent of the sunlight.

The oceans heat up, and Arctic temperatures rise further.

A small temperature increase at the poles leads to still greater warming over time, making the poles the most sensitive regions to climate change on Earth.

According to scientific measurements, both the thickness and extent of summer sea ice in the Arctic have shown a dramatic decline over the past thirty years. This is consisistent with observations of a warming Arctic.

The loss of sea ice also has the potential to accelerate global warming trends and to change climate patterns.

For more on the ways sea ice interacts with other Earth systems, including global ocean circulation, people, and animals, see All About Sea Ice: Environment.

Why Does the Melting of Arctic Sea Ice Matter?

The 2012 Arctic sea ice minimum, on September 16, 2012, reached the lowest ice extent in the satellite record. Credit: National Snow and Ice Data Center

What is sea ice extent, and why do you monitor that particular aspect of sea ice?

Sea ice extent is a measurement of the area of ocean where there is at least some sea ice. Usually, scientists define a threshold of minimum concentration to mark the ice edge; the most common cutoff is at 15 percent. Scientists use the 15 percent cutoff because it provides the most consistent agreement between satellite and ground observations.

Scientists tend to focus on Arctic sea ice extent more closely than other aspects of sea ice because satellites measure extent more accurately than they do other measurements, such as thickness. For more on sea ice extent, see Frequently Asked Questions About Arctic Sea Ice: “What is the difference between sea ice area and extent?”

What is the Arctic sea ice minimum?

The Arctic sea ice minimum marks the day, each year, when the sea ice extent is at its lowest. The sea ice minimum occurs at the end of the summer melting season.
The summer melt season usually begins in March and ends sometime during September. The sea ice minimum has been occurring later in recent years because of a longer melting season.

However, ice growth and melt are local processes; sea ice in some areas will have already started growing before the date of the sea ice minimum, and ice in other areas will still shrink even after the date of the minimum.

Changes in the timing of the sea ice minimum extent are especially important because more of the sun's energy reaches Earth's surface during the Arctic summer than during the Arctic winter.

As explained above, sea ice reflects much of the sun's radiation back into space, whereas dark, ice-free ocean water absorbs more of the sun's energy. So, reduced sea ice during the sunnier summer months has a big impact on the Arctic's overall energy balance.

For more information on current sea ice conditions see the Arctic Sea Ice News & Analysis Web page. To read NSIDC press releases on past Arctic sea ice minima, see the Arctic Sea Ice Press Announcements Archive on the Arctic Sea Ice News & Analysis Web page.

Why Does the Melting of Arctic Sea Ice Matter?

Seen from January through December, this timeseries shows the natural waxing and waning of the Arctic sea ice cover with the seasons.

The maximum extent generally occurs in March, the minimum extent in September.

Sea ice extent in 2015 (blue) fell well below the 1981 to 2010 long-term average (gray) and was  above 2012 (dotted light green), in which the lowest summer minimum to date occurred. Credit: NSIDC

What is the Arctic sea ice maximum?

The Arctic sea ice maximum marks the day of the year when Arctic sea ice reaches its largest extent. The sea ice maximum occurs at the end of the winter cold season.
The Arctic cold season usually begins in September and ends in March.

Monitoring winter sea ice is important to understanding the state of the sea ice. Scientists have found that Arctic sea ice has been recovering less in the winter, meaning the sea ice is already “weak” when the summer melting season arrives.

A possible cause is that the underlying ocean is warmer.

To read NSIDC press releases on past Arctic sea ice maxima, see the Arctic Sea Ice Press Announcements Archive on the Arctic Sea Ice News & Analysis Web page

How do scientists monitor the Arctic sea ice?

Obtaining reliable measurements of sea ice as it changes was difficult until the satellite era began in the early 1970s.

To monitor Arctic sea ice, NSIDC primarily has used the NASA Advanced Microwave Scanning Radiometer–Earth Observing System (AMSR-E) instrument on the NASA Aqua satellite and the Special Sensor Microwave/Imager (SSM/I) instrument on the Defense Meteorological Satellite Program (DMSP) satellite.

The satellites pass over the polar region several times each day to gather data; researchers can then form the data into images for analysis and publication. Because the AMSR-E instrument is no longer functioning, NSIDC now relies on DMSP data.

Useful satellite data concerning sea ice began in late 1978 with the launch of NASA's Scanning Multichannel Microwave Radiometer (SMMR) satellite. When scientists compare average sea ice conditions between years, they often use a 30-year reference period of 1981 to 2010. This reference period allows a consistent comparison of changes in extent over individual years.

To learn more about studying sea ice, see All About Sea Ice: Studying; to explore the satellite-derived sea ice images, see the Sea Ice Index.

Is Antarctic sea ice important, too? Is it shrinking?

Why Does the Melting of Arctic Sea Ice Matter?

Strong winds caused sea ice to crack and buckle off the coast of Greenland. Credit: Andy Mahoney, NSIDC

Scientists monitor both Arctic and Antarctic sea ice, but Arctic sea ice is more significant to understanding global climate because much more Arctic ice remains through the summer months, reflecting sunlight and cooling the planet.

Sea ice near the Antarctic Peninsula, south of the tip of South America, has recently experienced a significant decline. The rest of Antarctica has experienced a small increase in Antarctic sea ice.

Antarctica and the Arctic are reacting differently to climate change partly because of geographical differences. Antarctica is a continent surrounded by water, while the Arctic is an ocean surrounded by land.

Wind and ocean currents around Antarctica isolate the continent from global weather patterns, keeping it cold.

In contrast, the Arctic Ocean is intimately linked with the climate systems around it, making it more sensitive to changes in climate.

For more information about Antarctic sea ice, see All About Sea Ice: Arctic vs. Antarctic. Also read Frequently Asked Questions About Arctic Sea Ice: “Why don't I hear much about Antarctic sea ice?”

Where can I learn more?

NSIDC ResourcesArctic Sea Ice News & Analysis. Follow current sea ice conditions with monthly updates and analysis.Frequently Asked Questions about Arctic Sea Ice.

Read scientist answers to common questions regarding Arctic sea ice.All About Sea Ice. This educational site covers many aspects of sea ice.State of the Cryosphere: Sea Ice.

Learn how sea ice has changed in recent years.

NSIDC distributes scientific data sets related to sea ice. See Sea Ice Products at NSIDC to learn more about our data holdings.

Five reasons why the speed of Arctic sea ice loss matters

One of the most stark indicators of rising global temperatures has been the rapid decline of Arctic sea ice. For example, since the satellite data record began in 1978, average sea ice extent in September has decreased by around 13% per decade.

The pace of ice melt has increased attention on when the Arctic might see its first “ice-free” summer. (By “ice-free”, scientists usually mean a sea ice extent of less than one million square kilometres, rather than zero sea ice cover.

) How quickly this arrives will depend on the success of measures to cut global greenhouse gas emissions in order to slow rising temperatures.

 Climate model simulations suggest an ice-free summer could occur somewhere between 2032 and 2058 under high or medium emissions scenarios.

But why does it matter how quickly it happens? And what are the wider implications of melting sea ice?

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1. Loss of ice means more heat is absorbed

Albedo is a measure of how well a surface reflects sunlight. Snow-covered sea ice has a high albedo and reflects 85% of sunlight. But the open water revealed as ice melts is darker and absorbs more – reflecting just 7%. The less sunlight the Earth’s surface reflects, the more heat the planet absorbs.

Why Does the Melting of Arctic Sea Ice Matter?

The albedo effect in the Arctic. Source: NASA

Prof Jennifer Francis from Rutgers University explained recently that losing reflective sea ice can, in turn, speed up surface warming – what’s known as a positive feedback. She says:

“As sea ice retreats, sunshine that would have been reflected back to space by the bright ice is instead absorbed by the ocean, which heats up, melting even more ice.”

The heat doesn’t only warm the oceans. Francis explains excess heat entering the oceans during summer is later released back into the atmosphere – raising atmospheric temperatures too. It is one important reason why the Arctic is warming faster than the rest of the planet.

2. Melting Greenland ice sheet raises sea levels

In fact, the loss of reflective sea ice is one of the main reasons why Arctic temperature has risen three times faster than the global average in recent decades. This effect, known as “Arctic amplification”, has consequences for nearby land ice, too.

As land ice melts, it adds freshwater to the oceans causing sea levels to rise, and surface melt from Greenland is increasing, as the image below shows. Satellite data suggest over the last 20 years, the Greenland ice sheet has lost 140bn tonnes of ice per year.

This has raised sea levels by about 7.8 millimetres – 12% of total sea level rise in that time. Climate models project that by 2100, Greenland’s ice sheet could contribute four to nine centimetres to sea level. Earlier estimates had put that figure anywhere between one and 12 centimetres.

Why Does the Melting of Arctic Sea Ice Matter?

Number of melt days on the Greenland ice sheet on average (1979-2007) and last year (2018). Source: National Snow and Ice Data Centre

  • Warmer, sea ice free oceans could also increase melting from Greenland’s glaciers. Prof Andrew Shepherd from Leeds University tells Carbon Brief:
  • “[S]mall increases in ocean temperature can quickly destabilise glaciers that flow into the oceans, and so we could expect further ice losses due to that effect too.”

How does sea ice affect global climate?

Why Does the Melting of Arctic Sea Ice Matter?

Sea ice in the Arctic Ocean. While sea ice exists primarily in the polar regions, it influences the global climate.

Sea ice also affects the movement of ocean waters. The ocean is salty and when sea ice forms, much of the salt is pushed into the ocean water below the ice, although some salt may become trapped in small pockets between ice crystals.

Water below sea ice has a higher concentration of salt and is denser than the surrounding ocean water, so it sinks and moves from the surface. In this way, sea ice contributes to the circulation of the global ocean conveyor belt.

Cold, dense polar water descends from the surface and circulates along the ocean bottom toward the equator, while warm water from mid-depth to the surface travels from the equator toward the poles.

Why Does the Melting of Arctic Sea Ice Matter?

Sea ice is frozen water that forms, expands, and melts in the ocean. It is different from icebergs, glaciers, ice sheets, and ice shelves, which originate on land.

For the most part, sea ice expands during winter months and melts during summer months, but in certain regions, some sea ice remains year-round.

About 15 percent of the world's oceans are covered by sea ice during part of the year.

While sea ice exists primarily in the polar regions, it influences the global climate. The bright surface of sea ice reflects a lot of sunlight out into the atmosphere and, importantly, back into space. Because this solar energy “bounces back” and is not absorbed into the ocean, temperatures nearer the poles remain cool relative to the equator.

When warming temperatures gradually melt sea ice over time, fewer bright surfaces are available to reflect sunlight back into the atmosphere. More solar energy is absorbed at the surface and ocean temperatures rise.

This begins a cycle of warming and melting.

Warmer water temperatures delay ice growth in the fall and winter, and the ice melts faster the following spring, exposing dark ocean waters for a longer period the following summer.

Changes in the amount of sea ice can disrupt normal ocean circulation, thereby leading to changes in global climate.  Even a small increase in temperature can lead to greater warming over time, making the polar regions the most sensitive areas to climate change on Earth.

Arctic melt: Threat beneath the ice

Why Does the Melting of Arctic Sea Ice Matter?

Fram Strait, Arctic Circle (CNN)It's spring in the Arctic, and nature in the far north is just waking up, warmed by 24 daily hours of sunlight.

Here, in the waters of the Fram Strait, between Svaalbard and Greenland, is where ice comes to die.

The Arctic is heating up twice as fast as the global average, causing massive melting of sea ice. But while we know climate change is warming the Arctic air, there is a lot more happening under the ice that we don't fully understand.

A team of interdisciplinary scientists is here on a study facilitated by Greenpeace, at the start of the environmental group's nearly year-long pole-to-pole expedition. The scientists want to learn more about this threat beneath the ice, which could potentially destroy the cycle of life that starts here, and threaten the lives of people all over the planet.

  • The inflatable boats carrying the scientists maneuver slowly through a sea of fractured ice, a mosaic of pieces that once were part of the Arctic ice sheet, pushed south by winds and currents into the Fram Strait.
  • Here, the scientists spend days working on top of the precarious ice floes, keeping a watchful eye out for polar bears while drilling into the ice to measure its thickness.
  • “It has definitely thinned in this area, it has thinned everywhere” says team leader, polar physicist Till Wagner, of the University of North Carolina Wilmington.
  • Since 1990 the thickness of sea ice here has decreased by a third, from about 3 meters to 2 meters, according to the Fram Strait Arctic Observatory.

7 reasons why Arctic sea ice matters

“This year's minimum is relatively high compared to the record low extent we saw in 2012, but it is still low compared to what it used to be in the 1970s, 1980s and even the 1990s,” says Claire Parkinson, a climate change senior scientist at NASA's Goddard Space Flight Center, in a statement about the 2018 minimum.

Arctic sea ice always waxes and wanes with the seasons, but its average late-summer minimum is now shrinking by 13.2% per decade, according to the National Oceanic and Atmospheric Administration (NOAA).

And in its 2018 Arctic Report Card, NOAA reports the oldest Arctic sea ice — frozen for at least four years, making it more resilient than younger, thinner ice — is now in steep decline.

This oldest ice comprised about 16% of the total ice pack in 1985, NOAA reports, but it's now less than 1%, representing a loss of 95% in 33 years.

“A decade ago, there were vast regions of the Arctic that had ice that was several years old,” NASA researcher Alek Petty tells the Washington Post. “But now, that's a rare phenomenon.”

Scientists widely agree the main catalyst is human-induced climate change, boosted by a feedback loop known as Arctic amplification. (Antarctic sea ice, meanwhile, is more buffered against warming.) The basic problem has become well-known even among laypeople, thanks largely to its compelling effect on polar bears.

But while many people realize humans are indirectly undermining sea ice via global warming, there's often less clarity about the reverse of that equation. We know sea ice is important to polar bears, but why is either one important to us?

Such a question overlooks many other dangers of climate change, from stronger storms and longer droughts to desertification and ocean acidification. But even in a vacuum, the decline of Arctic sea ice is disastrous — and not just for polar bears. To shed some light on why, here are seven of its lesser-known benefits:

1. It reflects sunlight

The angle of sunlight, combined with albedo from sea ice, helps keep the poles cold. (Photo: NASA)

Earth's poles are cold mainly because they get less direct sunlight than lower latitudes do. But there's also another reason: Sea ice is white, so it reflects most sunlight back to space. This reflectivity, known as “albedo,” helps keep the poles cold by limiting their heat absorption.

As shrinking sea ice exposes more seawater to sunlight, the ocean absorbs more heat, which in turn melts more ice and curbs albedo even further. This creates a positive feedback loop, one of several ways warming begets more warming.

2. It influences ocean currents

The global conveyor belt of ocean currents, aka 'thermohaline circulation.' (Image: NASA)

By regulating polar heat, sea ice also affects weather worldwide. That's because the oceans and air act as heat engines, moving heat to the poles in a constant quest for balance.

One way is atmospheric circulation, or the large-scale movement of air. Another, slower method occurs underwater, where ocean currents move heat along a “global conveyor belt” in a process called thermohaline circulation.

Fueled by local variations in warmth and salinity, this drives weather patterns at sea and on land.

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Why Does the Melting of Arctic Sea Ice Matter?

Credit: Kathryn Hansen NASA Flickr (CC BY 2.0)Advertisement

Last week marked Arctic Matters Day hosted by the National Academy of Sciences. The free, public program highlighted results from research into the environmental changes happening in the remote region and how those changes will ultimately affect us all.

Last month, at a meeting of over 20,000 scientists from the American Geophysical Union, the National Oceanic and Atmospheric Administration (NOAA) issued an Arctic report card for 2015. Its marks were not good.

The maximum extent of arctic sea ice occurred two weeks earlier than in previous years and was the lowest on record. The sea ice that is present also turns out to be younger and thinner, with twice as much “first year” ice than was observed thirty years ago.

The report further notes the profound effects of this waning sea ice on the local habitat, including fish, walruses, and average sea temperatures.

NASA has released a video showing the difference between the current ice cover and the extent of the ice in years past. The largest difference is just north of Japan where the ice falls roughly 350 miles short of its past extent.

Due to the clear link to their diminishing habitat, polar bears have become the poster children for the direct impact of this lost Arctic sea ice. But how does this missing ice affect the rest of us? How are our futures connected to the future of the polar bear?

Here are six ways the impact of melting Arctic sea ice is already being felt in the Arctic and beyond.

»Continue reading on QuickAndDirtyTips.com

Arctic and Antarctic Sea Ice: How Are They Different? – Climate Change: Vital Signs of the Planet

We often get questions from readers about Earth’s sea ice in the Arctic and the Antarctic, and the differences between those areas. Arctic sea ice has declined over the past five decades, while Antarctic sea ice has increased, and then declined. Why do they behave differently?

How They’re Different

The primary difference between the Arctic and Antarctica is geographical. The Arctic is an ocean, covered by a thin layer of perennial sea ice and surrounded by land. (“Perennial” refers to the oldest and thickest sea ice.) Antarctica, on the other hand, is a continent, covered by a very thick ice cap and surrounded by a rim of sea ice and the Southern Ocean.

The Arctic Ocean is very deep and closely linked with the climate systems around it, making it more sensitive to climate changes than Antarctica.

During the centuries of human exploration in the Arctic, sea ice covered the Arctic Ocean well year-round, up until recent decades. But satellite observations show that Arctic sea ice has been declining in extent*, thickness and volume since 1979.1 Average Arctic sea ice extent is at its lowest since 1850.

During the summer melt season, the sea ice’s edge retreats toward the North Pole, only to re-grow during the Arctic winter. As a result of ongoing warming driven by human activities, the trend toward summer sea ice loss (from July to September, followed by a winter re-growth) continues.

Pollution is slowing the melting of Arctic sea ice, for now

The Arctic is one of the “canaries in the coal mine” for climate change. Long ago, scientists predicted it would warm quicker than other parts of the planet, and they were right.

Currently, the Arctic is among the fastest-warming places on the planet. Part of the reason is that as the Arctic warms, ice melts and ocean water is uncovered.

The ocean is darker than ice so it in turn absorbs more sunlight and increases its warming. This is a feedback loop.

Another reason is that the Arctic doesn’t get that much sunlight so increased energy from the atmosphere has a bigger influence there than it would have elsewhere.

Scientists have looked to the Arctic for clues and hints of human climate change over the past decades. The fact that the Arctic is warming has led to a 70% reduction in the volume of summer sea ice – an enormous loss of ice.

Decline in September Arctic ice extent (not volume). Illustration: Nasa

A recent paper just published in the Journal of Climate by the American Meteorological Society takes an in-depth look at how fast the Arctic ice is melting and why.

According to the paper, the authors completed a detection and attribution study of Arctic sea ice decline from 1953 to 2012. That is 60 years of data that tell the picture of climate change.

The “detection” part of this study was about detecting what long-term trends are apparent over these six decades. The “attribution” part of the study is figuring out what is the cause of the trends.

Why six decades? Well the authors wanted to go back as far as they could while still accessing high-quality records of the ice extent. They used three different sets of data that record the extent of ice in the region.

In terms of attribution, the authors looked for “fingerprints” of human activity. Humans emit greenhouse gases that trap heat. We know that and we have known that for a long time. Greenhouse gases make the Arctic warmer. But, other things are happening too.

There are natural changes to the Arctic. There are also other human pollutants that affect the ice. For instance, humans emit small particles called “aerosols” that can get into the atmosphere and block sunlight.

So, these human aerosol emissions can actually cause cooling.

The authors concluded that the combined cooling effect from human aerosols was detected in all three datasets of ice. That means, it didn’t matter whose measurements you used – the effect of aerosol cooling was present.

So how much of an effect do aerosols have? It turns out 23% of the warming caused by greenhouse gases was offset by the cooling from aerosols. Unfortunately, this isn’t good news. It means that if/when humans reduce our aerosol pollution, the warming in the Arctic and the ice loss there will be worse.

What an ice-free Arctic really means, and why it matters so much | CBC News

This story is part of a CBC News series entitled In Our Backyard, which looks at the effects climate change is having in Canada, from extreme weather events to how it's reshaping our economy.

At Earth's poles, ice and snow is disappearing — and it's transforming our planet. 

Snow and ice have long played a vital role in moderating Earth's climate. The white surfaces reflect the sun's radiation, which in turn helps maintain a comfortable temperature for life on the planet.

But with a warming planet, that ice melts or thins, exposing the dark water below, which absorbs that radiation. So each year the global temperature rises, melting more ice and snow.

It's a positive feedback loop: warming causes ice melt, ice melt causes warming.

And that process — also called Arctic amplification — leads to what we are observing now, which is a rapidly changing climate.

The Intergovernmental Panel on Climate Change (IPCC) Special Report on the Ocean and Cryosphere in a Changing Climate, released Wednesday, suggests that we could see an ice-free Arctic once every 100 years if we limit warming to 1.5 C above pre-industrial levels. If we warm to 2 C, that would increase to once every three years.

  • Could all that snow and ice at the poles eventually disappear altogether?
  • It's complicated.
  • The potential for an ice-free Arctic has been bandied about for decades, but it's important to know what scientists mean by “ice-free.”

“Usually when we talk about ice-free, it's virtually ice-free,” said Jennifer Francis, senior scientist at Woods Hole Research Center in Falmouth, Mass. “It's really during the late summer at the time when we usually see the minimum occur, which is right about now.”

Arctic Climate Change

Communicating a warming Arctic

WWF brings the effects of climate change in the Arctic to a global audience, and makes the connections between Arctic warming and global impacts.

Helping highly endangered seals

As Finland's climate warms, the country is seeing less snow cover. WWF is helping the extremely endangered Saimaa ringed sealsfind suitable places to nest by creating man-made snow banks.

Planning a future for the Last Ice Area

WWF is looking at the future management of the “Last Ice Area”, the place where summer sea ice is projected to persist longest.

Promoting renewable energy

WWF is advocating for renewable energy, and piloting renewable solutions with some Arctic communities.

Protecting the Last Ice Area in Greenland

The Last Ice Area will be essential as an enduring home for ice-dependent life. WWF-Denmark has made a proposal to include the Greenland section of the Last Ice Area on the tentative list for UNESCO world heritage.

Recommending action for walruses

The first circumpolar report on walrus conservation recommends research into the effects of industrial activities on the Arctic animals.

Surveying polar bears in Western Hudson Bay

WWF supports polar bear surveys using an innovative mark-recapture technique that does not require tranquilising the bears.

Teaching the next generation

WWF works with Students on Ice to provide high school students a first hand experience of the effects of climate change in the Arctic.

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