Due to the uproar over the subject of Global Warming I've decided to make this site available to anyone who has curiosity over the subject but doesn't want to get involved in the mudslinging, evasive tactics and length of time it takes to respond. Unfortunately you will have to scroll down (a long ways) to get to many subjects of interest as the links do not work properly. If anyone has the skills to clean up its messiness please feel welcome to do so.
villabolo
Frequently Asked Questions about Arctic sea iceBelow are some common questions we have received concerning Arctic sea ice. If you do not see your question answered here, please see: Studying sea iceIs Arctic sea ice really declining?Yes, the data show that Arctic sea ice really is in a state of ongoing decline. The reason we know this is because satellites offer us a long-term record. As of September 2007, the September rate of sea ice decline since 1979 was approximately -10 percent per decade, or 72,000 square kilometers (28,000 square miles) per year. Although the 2009 sea ice minimum was larger than the past two years, the rate of decline since 1979 increased to -11.2 percent per decade. September is the month that Arctic sea ice melts back to its lowest point, known as the annual minimum, and is an important indicator of overall ice conditions. However, sea ice in the Arctic is in decline in all months and the decline is greater and the rate faster than natural causes could account for. For more on the basics of sea ice, read Quick Facts on Arctic Sea Ice. Is Arctic sea ice starting to recover?In 2008, Arctic sea ice reached a minimum extent that was about 10 percent greater than the record low of 2007, and the minimum extent in 2009 was greater than either 2007 or 2008. Does this mean that Arctic sea ice is beginning to recover? Even though the extent of Arctic sea ice has not returned to the record low of 2007, the data show that it is not recovering. To recover would mean returning to within its previous, long-term range. Arctic sea ice in September 2008 remained 34 percent below the average extent from 1979 to 2000, and in September 2009, it was 24 percent below the long term average. In addition, sea ice remains much thinner than in the past, and so is more vulnerable to further decline. The data suggest that the ice reached a record low volume in 2008, and has thinned even more in 2009. Sea ice extent normally varies from year to year, much like the weather changes from day to day. But just as one warm day in October does not negate a cooling trend toward winter, a slight annual gain in sea ice extent over a record low does not negate the long-term decline. In addition, ice extent is only one measure of sea ice. Satellite measurements from NASA show that in 2008, Arctic sea ice was thinner than 2007, and likely reached a record low volume. So, what would scientists call a recovery in sea ice? First, a true recovery would continue over a longer time period than two years. Second, scientists would expect to see a series of minimum sea ice extents that not only exceed the previous year, but also return to within the range of natural variation. In a recovery, scientists would also expect to see a return to an Arctic sea ice cover dominated by thicker, multiyear ice. Why don't I hear much about Antarctic sea ice? What was sea ice like before the satellite era?The satellite record only dates back to 1979. However, scientists have used historical records of sea ice conditions to estimate sea ice extent before 1979. To extend the satellite record back to 1953, scientists have used shipping records and ice charts from several countries in combination with satellite data. One such record, called the Hadley data set, indicates that Arctic sea ice has been declining since at least the mid-1950s. To view a graph derived from the Hadley data set, please see State of the Cryosphere: Sea Ice. Before 1953, the historical record is less reliable. Shipping records go back to the 1700s, but only for limited areas and dates, and they do not always provide information about Arctic sea ice conditions. However, scientists do know that the Arctic was generally cooler up through the 1950s compared to recent years; the exception is a period during the 1930s and 1940s that was warmer than surrounding decades but still not as warm as recent years. Sea ice in the 1930s and 1940s was probably lower than it was during the 1950s. However, analysis of limited sea ice records from Russian ice charts indicates that while sea ice conditions were low, they were likely not as low as they have been during the 2000s. Plus, the trend in the 1930s and 1940s was both seasonal and regional in nature. The current decline touches all parts of the Arctic and affects all four seasons. To reconstruct sea ice history before the 1700s, scientists rely on ice cores and other methods to build a general idea of climate conditions. A broad understanding of climate helps scientists determine what sea ice conditions may have been like hundreds of years ago. Related questions: Has the Arctic Ocean always had ice in summer?We know for sure that at least in the distant past, the Arctic was ice-free. Fossils from the age of the dinosaurs, 65 million years ago, indicate a temperate climate with ferns and other lush vegetation. Based on the paleoclimate record from ice and ocean cores, the last warm period in the Arctic peaked about 8,000 years ago, during the so-called Holocene Thermal Maximum. A recent study suggests that 5,500 years ago, the Arctic had substantially less summertime sea ice than today. However, it is not clear that the Arctic was completely free of summertime sea ice during this time. The last time that scientists can say confidently that the Arctic was free of summertime ice was 125,000 years ago, during the height of the last major interglacial period, known as the Eemian. Temperatures in the Arctic were warmer than now and sea level was also 4 to 6 meters (13 to 20 feet) higher than it is today because the Greenland and Antarctic Ice Sheets had partly melted. Because of the burning of fossil fuels, global averaged temperatures today are getting close to the maximum warmth seen during the Eemian. Carbon dioxide levels now are far above the highest levels during the Eemian, indicating there is still warming to come. According to analyses at NASA, 2007 was the second-warmest year globally in the instrumental record; the Arctic was especially warm. Related question: Will the ice at the North Pole melt?Sometimes in everyday use, people associate “the North Pole” with the entire Arctic region. However, when scientists discuss the North Pole, they mean the geographic North Pole, a single point on the globe located at 90 degrees North. The term “Arctic” generally refers to a much larger region that encompasses the northern latitudes of the globe. The Arctic includes regions of Russia, North America, and Greenland, as well as the Arctic Ocean. Early in the summer of 2008, there were reports that the ice at the North Pole may melt away completely during the summer of 2008. While the possibility existed that the geographic point at the North Pole could be ice-free in summer at some point, NSIDC scientists did not made an official statement as to whether this might happen. The scientific community has a range of predictions concerning when we could see an ice-free Arctic Ocean in summer. It could be as early as 2013 or as late as 2100. NSIDC’s projections generally fall somewhere in the lower half of this range. Related questions: Why don’t I hear much about Antarctic sea ice?NSIDC scientists do monitor sea ice in the Antarctic, and sea ice in the Antarctic is of interest to scientists worldwide. While many have published peer-reviewed journal articles on the topic, it has received less attention than the Arctic. There are several reasons for this. Unlike Arctic sea ice, Antarctic sea ice disappears almost completely during the summer, and has since scientists have studied it. Earth’s climate system over thousands of years has been "in tune" with this annual summertime disappearance of Antarctic sea ice. However, satellite records and pre-satellite records indicate that the Arctic has not been free of summertime sea ice for at least 5,500 years and possibly for 125,000 years. So Earth’s climate system and ecosystems, as they exist today, did not develop in conjunction with an ice-free Arctic. Such an ice-free Arctic summer environment would be a change unprecedented in modern human history and could have ramifications for climate around the world. In March 2008, Antarctica experienced a record maximum. For more information, read Is wintertime Antarctic sea ice increasing or decreasing? Is wintertime Antarctic sea ice increasing or decreasing?Wintertime Antarctic sea ice is increasing at a small rate and with substantial natural year-to-year variability in the time series. While Antarctic sea ice reached a near-record-high annual minimum in March 2008, this does not indicate a significant long-term trend. To borrow an analogy from sports, one high day, month, or even year of sea ice is no more significant than one early-season win would be in predicting whether the hometown team will win the Super Bowl ten seasons from now. Another important point is that the increase in Antarctic sea ice extent is not surprising to climate scientists. When scientists refer to global warming, they don’t mean warming will occur everywhere on the planet at the same rate. In some places, temporary cooling may even occur. Antarctica is an example of regional cooling. Even our earliest climate models projected that Antarctica would be much slower in responding to rising greenhouse gas concentrations than the Arctic. In large part, this reflects the nature of the ocean structure in Antarctica, in which water warmed at the surface quickly mixes downward, making it harder to melt ice. In terms of sea ice, climate model projections of Antarctic sea ice extent are in reasonable agreement with the observations to date. It also appears that atmospheric greenhouse gases, as well as the loss of ozone, have acted to increase the winds around Antarctica. Perhaps counter intuitively, this has further protected the Antarctic from warming and has fostered more ice growth. The one region of Antarctica that is strongly warming is the Antarctic Peninsula, which juts out into the Atlantic Ocean and is thus less protected by the altered wind pattern. The Antarctic Peninsula is experiencing ice shelf collapse and strongly reduced sea ice. Finally, even if wintertime Antarctic sea ice were to increase or decrease significantly in the future, it would not have a huge impact on the climate system. This is because during the Antarctic winter energy from the sun is at its weakest point; its ability or inability to reflect the sun’s energy back into space has little affect on regulating the planet’s temperature. For more information, see All About Sea Ice: Arctic vs. Antarctic and the State of the Cryosphere: Sea Ice. To see data on Antarctic sea ice, see the Sea Ice Index. Related questions: What is the difference between sea ice area and extent?Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method. A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated. Extent defines a region as "ice-covered" or "not ice-covered." For each satellite data cell, the cell is said to either have ice or to have no ice, based on a threshold. The most common threshold (and the one NSIDC uses) is 15 percent, meaning that if the data cell has greater than 15 percent ice concentration, the cell is considered ice covered; less than that and it is said to be ice free. Example: Let's say you have three 25 kilometer (km) x 25 km (16 miles x 16 miles) grid cells covered by 16% ice, 2% ice, and 90% ice. Two of the three cells would be considered "ice covered," or 100% ice. Multiply the grid cell area by 100% sea ice and you would get a total extent of 1,250 square km (482 square miles). Area takes the percentages of sea ice within data cells and adds them up to report how much of the Arctic is covered by ice; area typically uses a threshold of 15%. So in the same example, with three 25 km x 25 km (16 miles x 16 miles) grid cells of 16% ice, 2% ice, and 90% ice, multiply the grid cell areas that are over the 15% threshold by the percent of sea ice in those grid cells, and add it up. You would have a total area of 662 square km (255.8 square miles). Scientists at NSIDC prefer to report extent because they are cautious about summertime values of ice concentration and area taken from satellite sensors. To the sensor, surface melt appears to be open water rather than water on top of sea ice. So, while reliable for measuring area most of the year, the microwave sensor is prone to underestimating the actual ice concentration and area when the surface is melting. To account for that potential inaccuracy, NSIDC scientists rely primarily on extent when analyzing melt-season conditions and reporting them to the public. That said, analyzing ice area is still quite valuable. Given the right circumstances, background knowledge, and scientific information on current conditions, it can provide an excellent sense of how much ice there really is "on the ground." Image and data questionsWhat is the gray circle in the middle of the extent map?Not all satellites pass close enough to the North Pole for their sensors to collect data there. This lack of data is indicated by a gray circle, or "pole hole," in each image. Related question: Then how will we know if ice at the North Pole melts?Historically, lack of satellite data directly over the North Pole has not concerned scientists; they have always assumed that the area underneath is covered with sea ice. However, in recent years, the possibility that there will be no sea ice over the North Pole in summer has become more likely. Fortunately, some satellite sensors are able to obtain data directly over the North Pole; Data from these satellites could be used to fill in data that are missing from other satellite records. For example, the NASA Advanced Microwave Scanning Radiometer—Earth Observing System (AMSR-E) could fill in some missing data because it has a smaller pole hole than other satellites. Or, scientists could use the NASA Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, which does collect data over the North Pole and thus has no pole hole. To learn more about how scientists study sea ice, see All About Sea Ice: Studying. Related questions: What satellite is the sea ice data from?The “Daily image update,” as well as many of the images shown in Arctic Sea Ice News & Analysis, are derived from the Sea Ice Index data product. The Sea Ice Index relies on NASA-developed methods to estimate sea ice conditions using passive-microwave data from the Defense Meteorological Satellite Program (DMSP) the Special Sensor Microwave Imager/Sounder (SSMIS). The basis for the Sea Ice Index is the data set, "Near-Real-Time DMSP SSM/I Daily Polar Gridded Sea Ice Concentrations," and the NASA-produced "Sea Ice Concentrations from Nimbus-7 SMMR and DMSP SSM/I Passive Microwave Data." For more details, see the Sea Ice Index. For information on the transition between the DMSP F13 satellite and the DMSP F17 satellite, see the June 2, 2009 post to Arctic Sea Ice News & Analysis. Why is the Sea Ice Index product used to study sea ice?The passive-microwave data used for the Sea Ice Index is especially helpful because the sensor can "see" through clouds and deliver data even during the six months of Arctic darkness and frequently cloudy conditions. Some other satellite sensors cannot penetrate clouds to take data, so the results are sporadic and dependent upon weather conditions. Still other sensors can see through clouds, but they do not cover the entire region of the globe where sea ice exists every day, making near-real-time monitoring difficult. Furthermore, some sensors cannot provide information in winter, when polar darkness prevails. The passive microwave sea ice record dates back to 1979, one of the longest environmental data sets we know of. This provides a long-term product that consistently tracks changes in the ice cover over many years, lending additional confidence to the trends that we observe. So, although NSIDC refers to additional satellite data in developing our analysis, we primarily rely on passive-microwave data for Arctic Sea Ice News & Analysis images and content, and for tracking long-term change. I know there is no ice where your image shows ice; why?Occasionally, our data images indicate ice where none actually exists. Why is this? One reason is that the images in our “Daily Image Update” have not yet undergone rigorous quality control to correct for conflicting information that is especially likely along coastlines. Another reason is that the data, in this case, are averaged over an area of 25 kilometers by 25 kilometers (16 by 16 miles). This means that a person may be looking at a small area with no ice that is next to or within an area that has ice. Other reasons that passive-microwave data may show ice where none actually exists on the ground include signal variation along coastlines between land and water, and atmospheric interference from rain or high winds over the ice-free ocean. In the daily extent data images, gaps (shown in dark gray in the extent map) are replaced with values interpolated from surrounding days, but temporary spurious results may occur. Despite the limitations in passive-microwave data products, they still yield quality estimates for the overall extent pattern and values of the ice. Plus, the limitations are consistent, affecting the data this year in the same way they have affected it in previous years. While passive-microwave data products may not show as much detail or be as accurate "on the ground" as other satellite data, they provide a consistent time series to track sea ice extent going back to 1979. This type of long-term, consistent data is important to scientists who study whether or not change is taking place in a system. To learn more about how scientists study sea ice, see All About Sea Ice: Studying. Other sources show ice where you don't; why?The data shown in the Arctic Sea Ice News & Analysis pages are usually from a passive-microwave sensor. The passive-microwave sensor records ice in 25 by 25-kilometer (16 by 16-mile) areas, which is lower resolution than other types of satellite sensors. This means that the ice edge could be off by as much as 25 to 50 kilometers (16 to 31 miles) in passive-microwave data compared to higher-resolution satellite systems. We define ice extent as anywhere with at least 15 percent ice. Thus it is possible that some ice could exist several kilometers beyond where our data show ice because overall, there is less than 15 percent over the full 25 by 25 kilometer area. Other reasons that passive-microwave data may not show ice where ice actually exists on the ground include the presence of thin, newly formed ice, the shift in albedo of actively melting ice, and atmospheric interference. Of particular note, thin, newly formed ice is consistently underestimated by the data used at NSIDC. However, such ice is important for operational centers such as the U.S. National Ice Center and the Canadian Ice Service. Those operational centers employ higher spatial resolution data that is better able to detect such thin ice. Despite the limitations in passive-microwave data products, they still yield quality estimates for the overall extent pattern and values of the ice. Plus, the limitations are consistent, affecting the data this year in the same way they have affected it in previous years. While passive-microwave data products may not show as much detail or be as accurate "on the ground" as other satellite data, they provide a consistent time series to track sea ice extent going back to 1979. This type of long-term, consistent data is important to scientists who study whether or not change is taking place in a system. To learn more about how scientists study sea ice, see All About Sea Ice: Studying. Related questions: Do your data undergo quality control?The daily and monthly images that we show in Arctic Sea Ice News & Analysis are near-real-time data. Near-real-time data do not receive the rigorous quality control that final sea ice products enjoy, but it allows us to monitor ice conditions as they develop. Several possible sources of error can affect near-real-time images. Areas near land may show some ice coverage where there isn’t any because a land filter has not yet been applied and the sensor has a coarse resolution. Sometimes, the data we receive have geolocation errors, which could affect where ice appears. Near-real-time data may also have areas of missing data, displayed on the daily map as gray wedges, speckles, or spider web patterns. In addition, satellite sensors occasionally have problems and outages, which can affect the near-real-time data. We correct these problems in the final sea ice products, which replace the near-real-time data in about six months to a year. Despite its areas of inaccuracy, near-real-time data are still useful for assessing changes in sea ice coverage, particularly when averaged over an entire month. The monthly average image is more accurate than the daily images because weather anomalies and other errors are less likely to affect it. Because of the limitations of near-real-time data, they should be used with caution when seeking to extend a sea ice time series, and should not be used for operational purposes such as navigation. To look at monthly images that have been through quality control, click on "Archived Data and Images" on the Sea Ice Index. What are the error bars for your images?NSIDC does not have error bars on the time series plot shown in the “Daily Image Update” and the daily time series plot (usually labeled “Figure 2”) because we strive to keep the images concise and easy to read. Plus, the error bars would be quite small compared to the total extent values in the images. We estimate error based on accepted knowledge of the sensor capabilities and analysis of the amount of “noise,” or daily variations not explained by changes in weather variables. For average relative error, or error relative to other years, the error is approximately 20,000 to 30,000 square kilometers (7,700 to 11,600 square miles), a small fraction of the total existing sea ice. For average absolute error, or the amount of ice that the sensor measures compared to actual ice on the ground, the error is approximately 50 thousand to 1 million square kilometers (19,300 to 386,100 square miles). The absolute error values may seem high, but it is important to note that each year has roughly the same absolute error value, so the decline over the long term remains clear. NSIDC has high confidence in sea ice trend statistics and the comparison of sea ice extent between years. For more on the importance of long-term trends to scientific study, see If Arctic sea ice is declining, why does your data show that this year has more ice than previous years? Related questions: Why do you use the 1979–2000 average for comparisons?NSIDC scientists use the 1979 to 2000 average because it provides a consistent baseline for year-to-year comparisons of sea ice extent. Scientists call this long-term average over a data series a “climatology.” If we were to recalculate the climatology every year to incorporate the most recent year of data, we couldn’t meaningfully compare between recent years. To borrow a common phrase, we would be comparing apples and oranges. The problem with relying on a sliding average becomes clear over time, when we try to compare new years of data with previous years. For example, if we rely on a standard, unchanging climatology like 1979 to 2000, we can easily and clearly compare September 2007 and September 2008 with each other. However, if we were to use the sliding climatology of 1979 to 2006 for September 2007, and the sliding climatology of 1979 to 2007 for September 2008, we would no longer be comparing “apples to apples” when we compared the two years to climatology. Finally, some scientists point out that since 2000, sea ice has declined precipitously. While you can do an average over any period, it is better to do so over a stable period, either a period of relatively flat change or cyclical change with little overall trend. If you include a strong increasing or decreasing trend when you calculate an average, you probably will not have a representative average. That said, NSIDC has recently considered revisiting the 1979 to 2000 average. We now have thirty years of Arctic sea ice data. A thirty-year time series is a widely accepted scientific standard for a climatology because it is long enough to encompass most cyclical patterns of natural variation. The problem, however, is that we would have to deal with the potential confusion caused any time that a standard is changed. The graphs would look different to the general public and would require a great deal of explanation. For those who are interested in comparing the thirty-year decline in Arctic sea ice extent to something different than the 1979 to 2000 average, the NOAA Arctic Report Card 2008: Sea Ice offers a graph showing groups of five-year averages from 1979 to 2008. What one immediately notices is that the overarching story remains the same: Arctic sea ice is rapidly declining over the satellite record, no matter how you calculate the averages. Related questions: The daily image update isn't current; why?The daily image update is produced from near-real-time operational satellite data, with a data lag of approximately one day. However, visitors may notice that the date on the image is occasionally more than one day behind. Occasional short-term delays and data outages do occur and are usually resolved in a few days. Related question: Are there other sources of sea ice data? How do these sources differ from NSIDC data?Other researchers and organizations monitor sea ice independently, using a variety of sensors and algorithms. While these sources agree broadly with NSIDC data, extent measurements differ because of variation in the formulas (algorithms) used for the calculation, the sensor used, the threshold method to determine whether a region is “ice-covered,” and processing methods. NSIDC's methods are designed to be as internally consistent as possible to allow for tracking of trends and variability throughout our data record. Links to other sources of sea ice data are listed below:
Another source of sea ice data is the operational centers that provide support to ships navigating in the Arctic. There are often discrepancies between information from these centers and our data because they employ additional data sources to capture as much detail on sea ice conditions as possible. However, unlike our data, because the quality and availability of their data sources vary, their products do not provide a long-term, consistent timeseries suitable for tracking climate trends and variability. Several Arctic nations have operational sea ice centers. The two North American centers are:
Related question: What is standard deviation and how does it relate to sea ice extent?Standard deviation is a measure of variation around a mean. One standard deviation is defined as encompassing 68% of the variation, and two standard deviations encompass 95% of the variation. Scientists use standard deviations as a way to estimate the range of variability of data. In the context of climate data like sea ice extent, it provides a sense of the range of expected conditions. Measurements that fall far outside of the two standard deviation range or consistently fall outside that range suggest that something unusual is occurring that can't be explained by normal processes. For sea ice extent data, the standard deviation is computed for each day of the year from the extent on that day over the 22 years of the average climatology, 1979 to 2000. Doubling the standard deviation to produce a 95% range means that 95% of the daily extents for the years 1979 to 2000 fall within that range. In recent years, ice extent has declined and in the summer especially, it has regularly fallen outside of two standard deviations. This suggests that the recent decline in sea ice extent represents a significant change in conditions from 1979 to 2000 time period. Related question: Causes of global climate changeHow do we know human activities cause climate change?Fossil fuel burning is responsible for climate change because of the way in which an increased concentration of carbon dioxide in the atmosphere alters the planet’s energy budget and makes the surface warmer. The most fundamental measure of Earth’s climate state is the globally averaged surface air temperature. We define climate change as an extended trend in this temperature. Such a change cannot happen unless something forces the change. Various natural climate forcings exist. For example, periodic changes in the Earth’s orbit about the sun alter the seasonal and latitudinal distribution of solar radiation at the planet’s surface; such variations can be linked to Earth’s ice ages over the past two million years. Changes in solar output influence how much of the sun’s energy the Earth’s surface receives as a whole; more or less solar energy means warmer or cooler global climate. Explosive volcanic eruptions inject sulfur dioxide and dust high into the stratosphere, blocking some of the sun’s energy from reaching the surface and causing it to cool. These are climate forcings because they alter the planet’s radiation or energy budget. An increase in the atmosphere’s concentration of carbon dioxide is also a climate forcing: it leads to a situation in which the planet absorbs more solar radiation than it emits to space as longwave radiation. This means the system gains energy. The globally averaged temperature will increase as a result. This is in accord with a fundamental principle of physics: conservation of energy. As humans burn fossil fuels, adding carbon dioxide to the atmosphere, globally average temperature rises as a result. For more information about the human contribution to climate change, visit:
Do sunspots cause climate change?Some people wonder if the reason the sea ice is declining and the planet is warming can be explained by sunspots, which are related to variations in the Sun’s energy output over time. While changes in the suns output can affect the Earth’s climate, the recent warming cannot be explained by changes in solar activity. For more detailed information about this question, visit:
Have undersea volcanoes caused the Arctic sea ice decline?A recent study discovered active volcanoes on the floor of the Arctic Ocean, and some people have wondered if they are causing sea ice to melt. While volcanic eruptions surely warmed the ocean in the immediate vicinity of the eruptions, the amount of heat they produced compared to the large volume of the Arctic Ocean is small. The Arctic Ocean covers 14 million square kilometers (5.4 million square miles), about 1 ½ times the size of the United States or 58 times the size of the United Kingdom. In its deepest spots, the Arctic Ocean is 4,000 to 5,500 meters (13,000 to 18,000 feet) deep. The heat from the volcanoes would have dispersed over an enormous volume and had little effect on ocean temperature, much as a bucket of boiling water emptied into a lake would have little effect on the lake's temperature. Second, the eruptions would have introduced heat deep below the sea ice that floats on the ocean surface. The tops of even the tallest undersea volcanoes are more than 1,000 meters (3,000 feet) deep. The Arctic Ocean is strongly stratified, which prevents layer mixing and makes it difficult for any deep water, even deep water warmed by heat from volcanoes, to reach the surface and melt the ice. This layering results from a strong density gradient: water layers near the surface are less salty and therefore less dense, while bottom waters are the densest. Unlike most oceans, where density gradients are determined by both salinity and temperature, Arctic Ocean waters are heavily stratified primarily because of variations in salinity. Do icebreakers contribute to climate change?When icebreakers travel through sea ice, they leave trails of open water in their wake. Dark open water does not reflect nearly as much sunlight as ice does, so sometimes people wonder if icebreakers speed up or exacerbate sea ice decline. In summer, the passages created by icebreakers do increase local summertime melting because the ships cut through the ice and expose new areas of water to warm air. However, the melt caused by an icebreaker is small and localized. Channels created by icebreakers are quite narrow and few in number compared to natural gaps in the ice. In winter, any openings caused by icebreakers will quickly freeze over again. So, scientists do not think that icebreakers play a significant role in accelerating the decline in Arctic sea ice. Do hurricanes in the Atlantic break up Arctic sea ice?NSIDC is not aware of any evidence that hurricanes in the Atlantic, or elsewhere on the planet, play a role in Arctic sea ice decline. Once Arctic sea ice is broken up, does it melt faster?Yes—waves, sea spray, winds, and melt ponds all affect sea ice. If the ice is broken up, the areas of open water between floes absorb a great deal of solar energy in summer. That energy can be transferred both to the sides of the floes and underneath the floes, promoting further melt. Wind direction is also important. Warm southerly winds can promote melt both because they bring warm air. Also, southerly winds move ice northward away from the coast. Storms and their associated sea spray can work to reduce the albedo, or reflectivity, of the ice, further increasing melt. Other effects of wind on sea ice either push the ice together, resulting in a smaller extent, or spread it out, resulting in larger expanses of sea ice at a lower density. These processes are known as convergence and divergence, respectively. Another interesting question is, are these processes captured in global climate models? Computer simulations do not capture the level of detail that these sorts of processes entail. For example, while all of the global climate models participating in the most recent Intergovernmental Panel on Climate Change report show a decline in Arctic sea ice over the period of available observations, none of them match the severity of the trends we actually observe. It may be that some of the more detailed melt processes are not being captured properly. If warm Arctic conditions suggest continued global warming, then why doesn't colder-than-usual weather in my region suggest global cooling?We note recent Arctic weather conditions in our reports because they help us understand if weather has affected the ice this season. The year’s weather conditions in the Arctic do not create or indicate climate warming, just as a cooler season in any region of the Earth does not mean that climate is cooling. One season’s weather could either speed up or slightly slow down the loss of Arctic sea ice this year, but it will not change the climate trend and the basic causes of warming. Climate is a measure of the average conditions over a long period of time, so it is a better way to tell if changes may be persistent. Climate records show that the Arctic has warmed substantially over the past decades. The Arctic continues to warm faster than any other region of the world. Global data still show the Earth to be warming on average. Scientists expected that the Arctic could warm faster than other places on Earth, because of the way the Arctic interacts with the global climate system. Arctic warming is a special concern, because it effects can speed up the warming of the whole Earth. The following Web sites have more information on the science of climate change:
Possible solutionsIs renewable energy the answer?Almost every study published in peer-reviewed scientific journals confirms that Earth’s climate is warming because of fossil fuel burning. People naturally wonder what other sources of energy we could use, with renewable energy often being the one they ask about. NSIDC scientists do not specialize in renewable energy, but the following non-NSIDC resources might be of use:
If we put white “styrofoam” in the ocean to replace sea ice, would it stop climate change?Resurfacing the Arctic Ocean with ice substitutes probably would not work to stop climate change. One reason is that the Arctic is a vast region. If we attempted to bring the Arctic back to long-term average levels of “ice,” we would need to add approximately 2.6 million square kilometers (1 million square miles) of foam to the Arctic Ocean. This would be the equivalent of covering Alaska and Texas, or ten United Kingdoms, with polystyrene foam. Studies would also need to be done concerning the environmental impact of introducing such vast quantities of a human-made substance in the ocean, the albedo difference between ice and foam, the longevity of the solution, the cost of such an effort, and the carbon dioxide emitted during foam production and placement. That said, even if foam were a viable solution that was immediately undertaken, it still would not halt climate change right away. The climate system already has some heating yet to be realized; it has not yet caught up with the effects of fossil fuel burning of past decades. People sometimes refer to this future heating as heat "in the pipeline.” In a way, this is similar to how a credit card works. We have already “spent” fossil fuels, but we have not yet “paid” the full charge in terms of temperature rise. So, even if we were to prevent any more ice from melting, the planet still has some additional warming on the horizon. Where can I learn more?I have a question that isn’t answered here. Who may I contact?General public: Contact NSIDC User Services |