Accessed January 2016. (2020). The area is measured in square miles. Despite occasional positive anomalies tied to natural variability in atmospheric circulation patterns, springtime Northern Hemisphere snow cover has declined. 3 Rutgers University Global Snow Lab. Terrestrial snow cover in the Arctic [in State of the Climate in 2017]. United States Environmental Protection Agency, Download related technical information PDF,, Community Connection: Ice Breakup in Two Alaskan Rivers. Across the Northern Hemisphere, the total area covered by snow during March and April—the end of the snow season for much of the mid-latitudes—has also shrunk over time. Scientists have been assessing global warming by looking at declining snow cover for decades. June snow cover each … Soc., 101 (8), Si–S429 Robinson, D.A. A short-term removal of the snow from the ice stimu- lated algal primary producers and subsequently heterotrophic bacteria. It shows the average date when snow first starts to cover the ground in the fall, the average last date of snow cover in the spring, and the length of time between them. August 14, 2020. Figure 2 uses the same method, but with average snow cover calculated for each season: spring (defined as March–May), summer (June–August), fall (September–November), and winter (December–February). as well as derived mapped products (USAF Snow/Ice Analysis, AMSU, AMSR-E, NCEP models, etc.) 2016. The extent of snow cover has varied from year to year. The average area covered by snow has ranged from 3.0 million to 3.6 million square miles, with the minimum value occurring in 1998 and the maximum in 1978 (see Figure 1). Bull. The shaded band spans from the first date of snow cover until the last date of snow cover. Rising temperatures across the U.S. have reduced lake ice, sea ice, glaciers, and seasonal snow cover over the last few decades. Snow has very high albedo, reflecting up to 90 percent of the sunlight it receives. Scientists agree, human-caused global warming is the dominant cause. Spring and summer snow cover can have a particularly important influence on water supplies. In this way, the overall amount of snow cover affects patterns of heating and cooling over the Earth’s surface. 9 + more 24hr Snow Forecast. Now, satellites provide daily maps of snow cover for both hemispheres. and surface observations. Other graphs show a negative trend, such as decreased snow cover in the Northern Hemisphere, and declining Arctic sea ice, both of which are indicative of global warming. Findings include a negative … The NSA are based on modeled snow pack characteristics that are updated each day using all operationally available ground, airborne, and satellite observations of snow water equivalent, snow depth, and snow cover. The evidence for low-latitude glacial deposits during the supposed snowball Earth episodes has been reinterpreted via the concept of inertial interchange true polar wander (IITPW). Area of extent data: North America (no Greenland). Arctic sea ice reaches its minimum each September. Northern Hemisphere (NH) snow cover observed by satellite over the 1966 to 2005 period decreased in every month except November and December, with a stepwise drop of 5% in the annual mean in the late 1980s. Between 1966 and 2010, the amount of land and sea ice that is snow-covered each year has decreased over many Northern Hemisphere regions, especially during the spring snowmeltseason. The dotted line in fall is the time series of September‐mean sea ice area (reversed axis, × 10 6 km 2); in winter the JFM Arctic Oscillation Index, and in summer the northern hemisphere snow cover for May (reversed axis, × 10 7 km 2). 1 Harpold, A.A., and N.P. Although satellite-based snow cover maps are available starting in the mid-1960s, some of the early years are missing data from several weeks during the summer, which would lead to an inaccurate annual average. In managed watersheds, earlier melting of snow can change when and how much water is available for various uses. Figure 3 focuses on the contiguous 48 states plus Alaska. Do you have feedback to offer on this or another article?Let us know what you think. The results show a decrease in terrestrial snow cover fraction in fall (delayed snow cover onset) and spring (earlier snow melt), generating a shortening of the snow season. Decreases in snow cover have largely occurred in spring and summer, whereas fall and winter snow cover have remained fairly steady over the time period studied (see Figure 2). In fact, a new study by Flanner et al. Area of extent data: North America (no Greenland). United States Department of Agriculture National Resources Conservation Service, SNOTEL Data Collection Network Fact Sheet. This indicator measures the amount of land in North America that is covered by snow. Since 1972, the U.S. snow cover season has become shorter by nearly two weeks, on average (see Figure 3). 4 NOAA (National Oceanic and Atmospheric Administration). More snow means more energy reflects back to space, resulting in cooling, while less snow cover means more energy is absorbed at the Earth’s surface, resulting in warming. Sensitivity of soil water availability to changing snowmelt timing in the western U.S. Geophysical Research Letters 42(19):8011–8020. On a larger scale, runoff from melting snow feeds streams and rivers that supply water for agriculture and cities. Decreased Snow Cover Satellite observations reveal that the amount of spring snow cover in the Northern Hemisphere has decreased over the past five decades and the snow is melting earlier. These data cover all of North America (not including Greenland). Northern Hemisphere continental snow cover extent [in Blunden, J. and D. S. Arndt, Eds., 2020: State of the Climate in 2019., SNOTEL Data Collection Network Fact Sheet, 2013 Arctic Report Card: Spring snow cover below average again, Record Low Spring Snow Cover in Northern Hemisphere 2012, Winter 2012-2013 In Review, Western Snowpack and Water Supply (VIDEO), State of the Climate: 2011 Snow Cover in Northern Hemisphere, Reporting on the State of the Climate in 2018, At end of spring 2014, Northern Hemisphere snow cover below average for tenth year in a row, State of the Climate: 2011 Sea Surface Temperature. Snow cover refers to the amount of land covered by snow at any given time. Sea ice extent provided by the National Snow and Ice Data Center (NSIDC) is available from 1979–2020 for the Northern Hemisphere, Southern Hemisphere, and Globe. In the cold season, these Arctic birds burrow under an insulating layer of snow that piles up in willow thickets. By far the largest change has taken place in the spring, with the last day of snow shifting earlier by 19 days since 1972. As snow cover declines, dark soils and vegetation absorb more of the Sun’s energy. This map displays current snow depth according to the National Oceanic and Atmospheric Administration (NOAA) National Snow Analyses (NSA). In the Southern Hemisphere, Amer. Rutgers University Global Snow Lab, Data History. These changes are driven by warmer temperatures and an associated modification of the elevation-dependent rainfall vs. snowfall ratios ( Mudryk et al., 2018 ). some regions, snow avalanches involving wet snow have increased (medium confidence), and rain-on-snow floods have decreased at low elevations in spring and increased at high elevations in winter (medium confidence). A willow ptarmigan mid-way between its brown summer and all-white winter plumage. Printer-friendly PDF of all text and figures. Records from the last five decades show that on average, spring snow is disappearing earlier in the year than it did in the past, with the most rapid declines in snow-covered area occurring in June, a month when, historically, Siberia, Alaska, and northern Canada remained partially snow covered. The overall “whiteness” of an object determines how much sunlight it reflects back into space. Because snow is white, it absorbs only a small portion of the sunlight that hits it (10 to 20 percent in the case of fresh snow), and it reflects the rest back to space. An official website of the United States government. To squeeze or stretch the graph in either direction, hold your Shift key down, then click and drag. The Storm Track image shows the forecast snowfall over the next 24 hours. (2011) has found that so far, snow cover is declining more rapidly … A 2016 analysis of satellite records also pointed to a broad pattern of decreasing snow cover across the Northern Hemisphere, particularly in the … Bulletin of the American Meteorological Society, 99(8), S87–S88. This trend is especially stark in the Northern Hemisphere where spring snow cover has declined rapidly. Historically, large parts of the high latitudes of the Northern Hemisphere were well covered with snow as late as June (blue areas). Accessed August 29, 2011. At regional and local scales, water resource managers, flood forecasters, and farmers are intensely interested in knowing how much water is in snow and when it will melt. Therefore, the earlier decrease in snow cover increases the amount of sunlight absorbed by Earth, and in turn, surface temperatures. These two figures cover all of North America, not including Greenland. This figure shows the timing of each year’s snow cover season in the contiguous 48 states and Alaska, based on an average of all parts of the country that receive snow every year. The negative long-term trends of SCE reveal recent shrinkage of snow cover in NH. The data for this indicator were provided by the Rutgers University Global Snow Lab, which posts data online at:, and the National Oceanic and Atmospheric Administration’s National Environmental Satellite, Data, and Information Service, which collects satellite measurements and compiles maps at: When averaged over the entire year, snow covered an average of 3.24 million square miles of North America during the period from 1972 to 2015 (see Figure 1). Figure 1 was created by analyzing weekly maps to determine the total extent of snow cover, then averaging the weekly observations together to get a value for each year. Knowing when and how quickly snow will turn to water is essential for forecasting if water from snowmelt will soak into the ground or cause flooding. Local Weather ... Probability - High Temperatures - Low Temperatures - Cloud Cover - Wind - Relative Humidity - Dewpoint - Snowfall SEASONAL FORECASTS - Temperature - … Thus, the indicator is restricted to 1972 and later, with all years having a full set of data. These snow cover season dates have been averaged over all parts of the country that regularly receive snow.Â. Humans and ecosystems also rely on snowmelt to replenish streams and groundwater. Everything else being equal, a gradual increase in global CO 2 would most likely bring about: a. an increase in surface air temperature b. a marked decrease in plant growth c. a decrease in evaporation from the earth's oceans In different phases of these back-and-forth patterns, some regions receive abnormally large or small amounts of snow. For example, some plants and animals rely on a protective blanket of snow to insulate them from sub-freezing winter temperatures. Sea ice in the Arctic has decreased dramatically since the late 1970s, particularly in summer and autumn. Data source: NOAA, 20154Web update: August 2016, Key Points | Background | About the Indicator | About the Data | Technical Documentation. Scientists are modeling how Earth's climate might change over the next 100 years, and the results suggest that snow will cover less of the planet, particularly over Europe and Asia. Between 1972 and 2015, the average portion of North America covered by snow decreased at a rate of about 3,300 square miles per year, based on weekly measurements taken throughout the year. As temperature and precipitation patterns change, so can the overall area covered by snow. Evidence of warming is also apparent in living (biological) systems such as changes in … Snow cover also keeps the soil moist, so if the snow melts away earlier in the spring, the soil may dry out sooner, which can stress plants and increase the risk of wildfire.1, This indicator tracks the area covered by snow since 1972, based on maps generated by analyzing satellite images collected by the National Oceanic and Atmospheric Administration.
2020 decreased snow cover evidence