PRO/CON: The world's getting warmer, can nuclear power help us?

By Tribune News Service, adapted by Newsela staff
02.05.16

PRO: Using more nuclear energy will stop greenhouse gases

Nuclear power plants produce energy by splitting apart the nucleus, or center, of atoms. When the nucleus is split, heat is released. That newly released energy is then used to produce electricity. In turn, that electricity is sent through a grid to light our homes and power our computers. 

Nuclear power is only one of many ways of producing electricity. However, it is superior to any other method for one important reason. It is the best way to produce carbon-free electric power. 

Carbon is in carbon dioxide and other gases. It is released or emitted when fuels like coal, gas or oil are burned. People burn these fuels to power cars and all sorts of machinery. 

Carbon-containing gases are the main cause of the so-called greenhouse effect. Once they are released through the burning of fuels, they remain in the atmosphere and trap heat, just as heat is trapped in a greenhouse. Over time, this has caused average global temperatures to rise. 

A Valuable Tool

The global increase in average temperature is known as climate change or global warming. It is putting the planet at risk. Polar ice caps are starting to melt, thereby causing ocean levels to rise. Increasingly, coastlines and island nations are being submerged. In other parts of the world, droughts are becoming common as lakes and rivers dry up.

The world is starting to come together to try to limit climate change. Clearly, a carbon-free source of energy like nuclear power is a valuable tool in that effort.

Nuclear power now accounts for more than 60 percent of the United States' zero-carbon electricity. It is playing an essential part in the battle to reduce greenhouse gas emissions.

Wind power and solar power can also produce energy without releasing carbon. However, they are not constant. To work, the sun has to be out, or the wind has to be blowing.

Nuclear power plants run 24 hours a day, seven days a week. They are the only constant source of power that does not emit greenhouse gases.

An Excellent Safety Record

Many claim nuclear power is dangerous. Nuclear power plants produce radiation, which can be a dangerous form of energy. Even a small amount can cause severe damage to living things. Nuclear plants are built to keep radiation from leaking out, but many people worry such leaking will happen anyway.

Actually, there is no reason for concern. The nuclear power industry has an excellent safety record. 

The first commercial nuclear reactor began producing electricity more than 50 years ago. In all that time, there has not been a single death or injury from a radiation-related nuclear power plant accident in the United States. 

Many other countries also successfully rely on nuclear power. In France, nuclear power supplies 75 percent of the electricity, with enough to spare to provide almost a quarter of the electricity in Europe. 

The picture is very different in China, the world’s biggest carbon polluter. There, nuclear energy provides only 2 percent of the power. Coal remains China’s main energy source, and its use is increasing not only in China but throughout Asia.

Last month, representatives of most of the world's nations met in Paris, France, to discuss the climate crisis. The agreement they signed was far-reaching. It set a goal of bringing carbon emissions down to zero by the second half of this century.

Meeting that goal might seem impossible. However, France and Sweden show that countries can change their energy use very quickly. Both have been able to greatly increase their use of carbon-fee nuclear power in a relatively short time.

Reducing The Need For Oil

If the world built nuclear reactors at the same rate as France and Sweden have, the effect would be enormous. In 25 to 34 years, all the electricity now produced though burning coal and natural gas could be produced by nuclear power.

During this period, electric vehicles powered by nuclear-generated electricity could dramatically reduce the need for oil. These changes would greatly lower global carbon emissions and would help prevent dangerous climate change.

Meeting the new climate control goals is a daunting challenge. The world’s population is expected to increase to more than 9 billion by 2040. As a result, global demand for electricity will nearly double.

Unless the use of nuclear power is greatly increased, it will be impossible to both meet future energy demand and prevent dangerous climate change. Nuclear power is the only way to achieve both those goals at the same time.

CON: Nuclear power is only part of the answer, we need more solar and wind energy

The 2015 Paris climate agreement sets a remarkable goal. It calls on all countries to greatly reduce their greenhouse gas emissions.

Most of these emissions come from the burning of fossil fuels like coal, oil and natural gas. The message could not be clearer: We need to change the way we generate and use energy, and do so quickly.

The United States set itself a modest goal. It has pledged to cut emissions by around a quarter by 2025. The country has already taken some steps to meet that goal, but much more is needed.

Perhaps the most realistic approach is to increase the use of both nuclear power and renewable energy. Renewable energy sources, also called renewables, include such things as wind power and solar power.

A Better Bet

China has been using this approach. It plans to double its nuclear power capacity, and has 24 new plants now under construction. However, it is also expanding its use of wind and solar power.

Should the United States do the same? Yes, but only in part. Currently, our 99 nuclear reactors only account for about 8 percent of the electricity the U.S. consumes. Most of the energy we use, about 81 percent, comes from fossil fuels.

Nuclear power will have an important part to play, but it is unlikely to replace much fossil fuel use. It is still too expensive and too risky.

A better bet is to expand the use of renewables, while also working to make our energy use less wasteful.

Globally, nuclear electricity production has been leveling off while wind and solar power are soaring. There are good reasons for this.

One is cost. The new nuclear plants now being built in the U.S. are expected to cost $8 billion to $9 billion each, possibly more. It is also very expensive to safely shut down plants, which eventually becomes necessary when they are too old.

These very high costs make it difficult for the private utilities that provide our electricity to increase nuclear power generation. They see more promise and lower costs in natural gas-powered plants or in turning to renewables.

Nuclear Waste, And A Disaster

The problem of radioactive waste is another big reason to avoid an increase in nuclear power. There is currently no acceptable way to dispose of the highly radioactive waste nuclear plants create. 

There is also always the chance of the kind of disaster that occurred in Fukushima, Japan. In 2011, an earthquake there caused radiation-contaminated water to leak out of a nuclear plant, poisoning the surrounding area. The U.S. public remains understandably concerned that such a disaster could happen here.

A better way is for the country to greatly increase its use of renewables. At the same time, we should try to use energy in a way that is less wasteful. A non-wasteful use of energy is known as energy efficiency.

There are many ways to cut down on wasteful energy loss. Among them are improved building design, and a greater use of trains and buses in place of cars. We should modernize our electrical grid, and design better lighting, heating and cooling systems.

The United States also should put more money into research on promising new types of energy.

The federal government has long favored nuclear power and fossil fuels. For the past 10 years, renewables and energy efficiency have begun to receive significant support. We should keep moving in that direction, and quickly.

Questions:

1. What are the advantages of using nuclear plant?

2. What are the disadvantages of using nuclear plant?

3. Which countries are currently using nuclear plant as their main power supply?

4. Define "renewables" and give a few examples.

5. In your opinion, should our country use nuclear power and why?

More than 1 million people sought refuge in Europe this year, report says

By Associated Press, adapted by Newsela staff

12.24.15

GENEVA, Switzerland — More than 1 million people entered Europe in this record-breaking year, migration experts said Tuesday. They were driven out of their home countries by war, poverty and persecution. This mass movement of people has challenged the idea of European unity.

With just days left in 2015, the International Organization for Migration (IOM) said 1,005,504 people had entered Europe as of Monday. The number was more than four times as many as last year. Almost all of them came by sea, and 3,692 people drowned trying to make the crossing.

European governments must make migration safer, said IOM official William Lacy Swing. He is general director of the organization. 

"We know migration is inevitable. It's necessary and it's desirable," Swing said. He added, "Migration must be legal, safe and secure for all — both for the migrants themselves and the countries that will become their new home."

Getting Accurate Count Is Hard

The IOM gets its the numbers from government records. The figures are from Greece, Italy, Bulgaria, Spain, Malta and Cyprus, spokesman Joel Millman said. He noted that the real number of people entering Europe may be even larger. Officials are having trouble getting an accurate number because so many have entered Europe in such a short time.

Most people entered Europe from Greece, which took in 820,000 people this year. Nearly all of them crossed from Turkey by boat across the Aegean Sea. Another 150,000 came into Italy across the Mediterranean Sea from north Africa, while smaller numbers crossed from Turkey by land into neighboring Greece and Bulgaria. Even fewer arrived by boat to other countries around the Mediterranean.

Not all the migrants are included in the IOM count. Others crossed into Europe across other borders. A few thousand people have crossed by bicycle from Russia to Norway.

Many People Drowned During Trek

About half of the people entering Europe were Syrians. Another 20 percent were Afghans, and 7 percent were Iraqis, IOM said.

Many fleeing war and persecution will likely be allowed to stay in Europe. Others who came to find work could be sent back.

Of the deaths, 2,889 were people traveling from North Africa toward Italy, the IOM said. A total of 706 drowned trying to cross the Aegean to Greece, and 72 died trying to reach Spain. No one knows exactly how many have died in shipwrecks or who they were. The bodies of others, including a 3-year-old child, have washed up on Greek beaches. This shocked the world and led European officials to promise to make the migration routes safer.

The war in Syria has been particularly important in the refugee crisis. The war has killed hundreds of thousands and has caused millions to flee. European governments have struggled to agree on how to handle the migrants. They have argued whether to welcome them at all and how best to care for the huge number of people.

Cold Weather Adds To Dangers

Over the summer, some Eastern European countries opened and closed their border, which caused confusion and frustration. Hungary, in particular, angered its neighbors by building a fence to keep people out. Migrants began rushing to find alternate routes through countries, which were unable to handle so many people. A more organized system began in the fall.

Germany and Sweden have welcomed the largest numbers of refugees. About 1 million migrants arrived in Germany this year, including large numbers of people from Eastern Europe who could be sent back.

With cold weather making journeys more dangerous, the number of migrants has slowed, but people are still showing up in Greece. Also, there's no sign that the number of migrants will go down when temperatures start rising again in the spring. IOM said more than 4,100 people arrived on the Greek islands on Monday alone.

Questions:

1. Why did people sought refugee?

2, How many refugee entered Europe in 2015?

3.Where in Europe does the people migrate to?

4.Explain two ways how refugees travel to Europe?

5. Where did the refugees come from?

6. What are the dangers that might be faced by the refugees during their travelling?

7. Do you think our country should welcome refugee? Why?

PRO/CON: Should we regulate e-cigs?

By Tribune News Service, adapted by Newsela staff

03.31.15

PRO: E-cigs shouldn't be banned, but they must be regulated

In 2014, the Oxford English Dictionary’s word of the year was “vape.” Simply put, it's breathing water vapor in and out through an electronic cigarette, or e-cigarette.

The Food and Drug Administration (FDA) should take a hint from the dictionary. It should write its own definition of e-cigarettes. They contain liquid nicotine, so the FDA should define them as a tobacco product.

Congress created the FDA in 1906. The government was concerned then over the quality and safety of America’s food and drug supply. 

The agency was created to help people know whether a product is safe and healthy.

In short, the FDA was made to watch over products just like e-cigarettes.

Nicotine Is Not Harmless

E-cigarettes claim to be healthy, but there is no proof. Right now more than 16 million children can legally buy e-cigs and give themselves as much nicotine as they want. Nicotine is not harmless. Accidentally drinking liquid nicotine has caused a huge increase in poisonings — including the death of a toddler in New York state two months ago.

Sales of e-cigs are booming. Last year, analysts at Wells Fargo bank estimated that sales of e-cigarette and other products amount to $2.5 billion a year. They predict it will rise to $10 billion annually by 2017.

The growth of e-cigs is partly due to advertising. Yet, the other reason is the growth in the number of high school students using them. The variety of e-cig flavors attract young people. Cotton candy, gummy bear and root beer float are just some of them.

E-cigs should be regulated, not banned. The FDA is the only agency that can do that. The FDA should prevent sales and advertising to kids. It should also make sure that health claims made by e-cig companies are true. Finally, it should require companies to list what's in e-cig juice.

“Juice” sounds harmless, but it's far from it. It is, in fact, flavored nicotine liquid. The liquid nicotine is heated through the e-cig and turned into vapor that users then inhale and exhale. At least, people inhale this flavored vapor and not burning tobacco. Because burning tobacco releases thousands of chemicals, e-cigs are safer than cigarettes.

Stop And Think

But, then again, cigarettes kill 6 million people per year. One historian called them the deadliest invention in human history.

And here is the possible value of the e-cigarette: it could be a powerful tool for saving millions of lives if smokers switched from puffing to vaping, and then to nothing.

The problem is that the safety and health claims of e-cigarettes have not been proven. Online, some folks claim e-cigs have helped them kick the habit, yet it might just be a few people.

Initial evidence from a major new study should make people stop and think. Early findings from the study of 46,000 Americans by the National Institutes of Health and the FDA indicate that smokers frequently use both e-cigarettes and regular cigarettes.

These findings agree with other studies that found that rather than helping people quit smoking, e-cigarettes may actually make it harder for smokers to quit.

Beware Of Advertising

Nevertheless, e-cigarettes are frequently advertised as if they've been proven to be healthy. Researchers at the University of California-San Francisco found that 95 percent of e-cig websites either made outright claims that they had health benefits, or hinted there were some. Sixty-four percent made claims directly related to helping users quit smoking.

This is false advertising. Nicotine is addictive and it is a poison. The FDA should make both of these facts clear by requiring warning labels on e-cigarettes and bottles of e-juices. Skin contact with even small quantities of liquid nicotine can cause dizziness, vomiting and seizures. Swallowing it can be deadly.

A world in which a dangerous product is marketed and sold as a healthy one is exactly what the FDA exists to prevent.

E-cigarettes are not snake oil. But gummy bear, cotton candy and sour apple shouldn’t make them any easier to use.

ABOUT THE WRITER: Sarah Milov is an assistant professor of history at the University of Virginia. She currently is writing a book about tobacco in the 20th century. Readers may write her at 435 Nau Hall South Lawn, Charlottesville, VA 22904.

This essay is available to Tribune News Service subscribers. Tribune did not subsidize the writing of this column; the opinions are those of the writer and do not necessarily represent the views of Tribune or Newsela.

CON: Inhaling e-cigarettes is not like smoking cigarettes

In 1964, the office of the Surgeon General — the top government doctor — released its very first report on tobacco smoking.

It looked at scientific evidence from more than 7,000 articles on smoking and disease. Based on those studies, the report cited tobacco smoking as a major cause of lung and throat cancer.

The report launched a “war on smoking.” It soon led to health warnings on cigarette packages and bans on cigarette commercials on radio and television. In recent years, it has led to bans on smoking in public places, like restaurants.

Over this half-century of cigarette regulation, two facts have been impressed upon the nation: 1) smoking tobacco kills people; 2) once a person is addicted to smoking cigarettes, or, rather, to the nicotine one ingests by smoking cigarettes, it is very hard for a person to quit.

An Anti-Smoking Aid

Then an invention came along — e-cigarettes. They supply nicotine in much the same way as a tobacco cigarette. Yet, they don't appear to cause cancer or lung disease. Many people cheered the new invention.

Finally there was a product that could help those who were addicted. People who had tried other ways of quitting now had another anti-smoking aid to try.

Lives could be saved. People could replace their tobacco cigarettes with e-cigarettes. Instead of inhaling smoke and all its carcinogens — like tar — they'd just breathe water vapor. And that horrible smell would be replaced with just the light scent of a flavor like mint or strawberry.

Lives could be saved.

One would expect the public health community to be cheering loudly — and some some health professionals have, in fact, been supportive of e-cigarettes.

But some people appear to be addicted to regulation, and not to public health. For them, e-cigarettes challenge their beliefs.

Too Many Worries?

How can they try to ban a product that saves lives?

Many of these regulators are worried about the “what ifs.” “What if” vaping turns out to be harmful? “What if” people who vape decide to start smoking?

These “what ifs” are quite unlikely. However, it is on the basis of them that some people support bans. Some want bans on the sale of e-cigarettes. Others want to add grossly high taxes on e-cigarettes to discourage people from using them. Some even want outright bans on the use of e-cigarettes in public.

But such policies mean nicotine addicts will be less likely to use e-cigarettes. Instead, they may be more likely to keep smoking tobacco, which would obviously lead to more tobacco smoking and thus, more illness and death.

"Different Levels Of Risk"

The director of the FDA’s Center for Tobacco Products, Mitch Zeller, made the key point clear: “People are smoking for the nicotine, but dying from the tar.”

He says e-cigarette regulation should take into account that different nicotine products "pose different levels of risk to the individual.” He believes they should be regulated according to their risks.

Which means America should not treat e-cigarettes and vaping just like tobacco smoking and smoke. Smoking is clearly far more dangerous than vaping.

In fact, vaping can cause people to voluntarily stop smoking. Because of that, we need carefully crafted rules. If they are well-written to steer Americans from smoking toward vaping as a replacement, it will provide “an extraordinary public health opportunity,” in Zeller's words.

Zeller makes a lot of sense. On the other side are the regulation nuts. These people are the enemy of public health.

Smoking kills. Vaping is a safer alternative. Our nation’s rules will save lives if they reflect this fact.

Questions:

1. What is e-cigs?

2. Is nicotine harmful to the body and how?

3. Why are high school students attracted to e-cigs?

4. How are e-cigs being advertised to the public?

5. What are the two facts of cigarettes impressed upon the nation?

6. In your opinion, should we regulate e-cigs and why?

7. How will the economic be affected by increase use of e-cigs? 

After losing huge amount, Greenland ice is melting faster than ever

By Washington Post, adapted by Newsela staff

01.05.16

A new study has calculated just how much ice Greenland has lost since the year 1900. The number is astounding: 9,103 gigatons.

A gigaton is a billion metric tons.  For reference, the Statue of Liberty weighs about 200 metric tons.

The study was completed by 16 authors and was published in the magazine Nature. The lead author was Kristian K. Kjeldsen of the Natural History Museum of Denmark at the University of Copenhagen. 

Estimating the loss of ice was not easy. It required the use of several information sources. These included the distinct marks left by retreating glaciers on the landscape, extensive aerial photography from 1978 through 1987, and satellite and aircraft observations beginning in 1983.

All were merged to provide the new ice loss estimates. "It's the first observational-based study that shows where Greenland has lost its mass over the last 110 years," said Kurt H. Kjær, the paper's senior author.

How Greenland Affects Earth's Waters

The study offers a better understanding of how Greenland's ice loss has contributed to sea level rise. As the global temperature has gradually increased, ice in Greenland and throughout the Arctic has started to melt.  The melting ice has added to the volume of the oceans. Oceans all over the world have been affected, with water creeping higher onto the land. The study measures the effect Greenland's melting ice has had on sea levels.

It shows that the ice in Greenland is starting to melt more quickly. The amount of total ice loss doubled from 2003 to 2010 compared to ice loss throughout the 20th century (1900-1999). During this recent time period, an average of 186 gigatons of ice melted each year. Other estimates have put that number even higher. NASA currently states that Greenland is losing 287 billion tons of ice per year.

The study notes that ice melted in Greenland throughout the 20th century. The authors suggest that around 1900, the Earth started coming out of the Little Ice Age, a natural cool period. As the planet started warming, some ice began to melt. 

Humans And Global Warming

However, the speed of ice loss increased rapidly as major human-caused global warming kicked in. Most scientists believe that the release of greenhouse gasses, caused by human activities, has led to a dangerous increase in the Earth's temperature.

Since 1900, the research finds, Greenland's major mass loss has been coming quite consistently from a few key regions. Much of the melting has come from the northwest and southeast of the ice sheet, the vast layer of ice that covers about 80 percent of Greenland. Ice has also been melting from the Jakobshavn glacier in the southwest, Greenland's single fastest moving glacier. It is currently losing 25 to 35 gigatons of ice annually.

However, in recent years, the northeast of the ice sheet has started to melt as well. It features two major glaciers named Zachariae Isstrøm and Nioghalvfjerdsfjorden, which hold back 12 percent of all of Greenland's ice.

The new research suggests that the ice melting in Greenland has had a major effect on the rising sea level. The study estimates that 9,103 gigatons of ice have been lost from Greenland in the last 110 years. That would amount to a 2.5 centimeter of sea level rise. In other words, if the new study is correct, ice loss in Greenland has added an inch to the world's oceans.

The Inch Felt Round The World

An inch may not sound like much, but spread over the entire globe it is a staggering and dangerous amount of water. If Greenland's ice keeps melting, it could lead to disaster. If the Greenland ice sheet were to melt, it would lead to roughly 20 feet of sea level rise.

The study also measured the amount of fresh water that has traveled into the North Atlantic ocean from Greenland and elsewhere. According to Jason Box, a professor with the Geological Survey of Denmark and Greenland, most of that melted water has probably stayed in the North Atlantic.

This could interfere with the Atlantic Ocean's water currents and circulation, which are driven by differences in temperature and saltiness. Cold salty water sinks in the North Atlantic and travels southward. This pulls more warm water north. If too much fresh water is added to the North Atlantic, however, it could slow or eventually shut down the circulation. This would have dramatic effects on the Earth's climate.

Keeping The Melt Under Control

The fact that so much ice in Greenland has melted, contributing fresh water to the oceans, is troubling, and the melting appears to be speeding up. The key for the future of Greenland's ice comes down to global warming. The big question is how high global temperatures will rise and how long they will stay there. 

Last month, world leaders met in Paris, France, and agreed to the goal of keeping warming well below 2 degrees Celsius (about 3.5 degrees Fahrenheit). If achieved, that may be enough to prevent all of Greenland's ice from melting.

However, if the Earth gets much warmer than that, Greenland's ice will not last. "The ice sheets are doomed in a plus-3-Celsius world," says Box.

Questions:

1. How much ice has Greenland lost since the year 1900?

2. Who led this study?

3. How did they estimate the lost of ice?

4. What is the cause of the ice melting?

5. What causes global warming?

6. In your opinion, what are the steps that could be taken to resolve this problem?

Animals that were oceans apart are now together, due to melting Arctic ice

By Washington Post, adapted by Newsela staff

12.21.15

Animals have been showing up in strange places lately.

Gray whales live in the Pacific Ocean. In the spring of 2010, though, a single gray whale was spotted in the Mediterranean Sea. It was the first time a gray whale was seen in the North Atlantic in about 200 years. 

How Did YOU Get HERE?

Other animals that live in the Pacific have been appearing in the Atlantic as well. Likewise, creatures that live in the Atlantic Ocean have been seen in the Pacific. 

What is going on? A group of scientists, led by a scientist named Seabird McKeon, published a paper about the strange pattern. The paper was released on Nov. 30 in the magazine Global Biology. It said that the reason animals are moving between the Atlantic and the Pacific may have to do with climate change. 

Between the Atlantic and Pacific are giant continents. Sea creatures cannot cross them. Connecting the two oceans to the north is the Arctic Ocean. The Arctic is one of the coldest places on earth. Because of how cold it is, big parts of the Arctic Ocean are covered in ice. 

Melting Ice Makes Travel Easier

The ice usually keeps animals from using the Arctic to move between the Atlantic and Pacific oceans. Animals like whales and seals have difficulty getting through the ice. It gets in the way of their swimming and can block them from coming up to breathe. Birds can fly over the frozen ocean, but the ice prevents them from diving for fish.

These days, however, the ice is starting to melt. The climate is changing. Each year, the earth is getting a little warmer. As the Arctic has warmed, ice has started melting. As a result, passageways have opened up in the ice. 

McKeon and his team believe that this has allowed certain animals to cross through the Arctic, letting them move between the Atlantic and the Pacific. It is like a bridge has opened up between two oceans that used to be separate. Animals that used to always be apart can now mix. Scientists call this mixing "faunal exchange."

Studying "Faunal Exchange"

Many animals could become part of the faunal exchange. Birds such as Arctic terns, common eiders, Atlantic puffins and short-tailed shearwaters may start to move between the Atlantic and the Pacific. Beluga whales, ringed seals and Atlantic white-sided dolphins may do so as well.

No one can say for sure what effects the faunal exchange will have. To get some idea, though, McKeon and his team examined past examples of faunal exchange.

The Great American Biotic Interchange was a large faunal exchange. Several million years ago a thin strip of land called the Isthmus of Panama formed between North and South America. The new bridge allowed land animals to cross between the two continents for the first time. As a result, animals from North America invaded South America. They beat out many of the native animals there for food. 

Watch Out For Killer Whales!

McKeon and his team also looked at what happened when killer whales moved into Hudson Bay, a large body of water in Canada. As their name suggests, killer whales are hunters. All of the sudden, the animals in Hudson Bay had to be on the lookout for a new predator. Faunal exchange, in that case, altered the delicate balance of predators and prey.

McKeon and his team argue that the current exchange between the Pacific and Atlantic may have the same kinds of effects. It may lead to genetic changes as well. As animals move to new territories, they mix with different kinds of animals. Sometimes these new neighbors interbreed. New kinds of animals might be born as a result.

What Next?

At this point, scientists can only wait and see, and study. Most scientists seem to agree that faunal exchange between the Pacific and Atlantic is already occurring. It seems like it will only increase as more passages open up in the Arctic. The effects of faunal exchange, however, remain to be seen.

Questions:

1. Where do gray whales live in and where were they found in now?

2. Why the animals are moving between the Atlantic and the Pacific?

3. Why do animals cannot cross between the Atlantic and Pacific?

4. Why does the ice keeps animals from using the Arctic to move between the Atlantic and Pacific oceans?

5. What does "faunal exchange" mean?

6. What are the effects of current exchange between the Pacific and Atlantic?