Earth Gauge » Ice

Climate Fact: Greenland’s Western Margin

administrator — Wed, 08 Oct 2008 21:41:20 +0000

Along the western margin of Greenland’s Ice Sheet, which is the second largest ice sheet in the world after Antarctica, melting is occurring at a rate of 2.5 meters (about eight feet) per year. The whole ice sheet itself moves towards the ocean at a rate of 100 meters (328 feet) per year, while the faster moving outlet glaciers, which are embedded into the ice sheet and discharge directly into the ocean, are moving at rates that vary from 200 to 12,000 meters (656 to 39,270 feet) per year. The loss of ice to the ocean exceeds the replacement of this ice by annual snowfall. Measurements taken in the summers of 2006 and 2007 in the area around Jakobshavn Ishbrae, Greenland’s largest outlet glacier, demonstrate the seasonality of this movement. During these two summers, the ice sheet as a whole moved 48 percent faster than its mean speed, while the area’s outlet glaciers moved 8.6 percent faster than their mean speed.

Seasons: Spring, Summer

Source: Joughin, Ian et al. “Seasonal Speedup Along the Western Flank of the Greenland Ice Sheet.” Science Express 17 April 2008, pp. 1-4, 1153288.

Climate Fact: Central Asia’s Glaciers

administrator — Wed, 08 Oct 2008 21:37:59 +0000

Central Asia, a general term for the landlocked region extending from the Caspian Sea eastward into China, has a growing and economically developing population that is largely dependent on glacial melt for its water supply. The Region’s glaciers, however, have been shrinking. In the Eastern Pamir Region of Tajikistan, for example, between 1978 and 1990, glaciers shrunk 7.8 percent and between 1990 and 2001, glaciers shrunk by 11.6 percent. In the Northern Tien Shan Mountain Range in Kyrgyzstan, glaciers have lost about 28 percent of their areal extent since the 1960’s. These glaciers provide water for parts of Kyrgyzstan, Kazakhstan, and China.

Seasons: Spring, Summer, Fall

Sources: Khromova, T. E. et al. “Changes in glacier extent in the eastern Pamir, Central Asia, determined from historical data and ASTER imagery.” Remote Sensing of the Environment 102 (2006): 24-32 and Niederer, P. et al. “Tracing glacier wastage in the Northern Tien Shan (Kyrgyzstan/Central Asia) over the last 40 years.” Climate Change 86 (2008): 227-234.

Climate Fact: Lake Baikal Trends

administrator — Wed, 08 Oct 2008 20:58:27 +0000

The Earth’s largest and oldest lake, Russia’s Lake Baikal, provides habitat for over 2,500 species, most of which are found nowhere else on Earth. Baikal has changed rapidly over the last 60 years. These changes include a two degree Fahrenheit rise in the temperature of the water, a corresponding 300 percent increase in chlorophyll concentration in the Lake, and a 335 percent increase in the zooplankton populations that feed on chlorophyll-producing algae. Additionally, the average number of days per year when ice covers Baikal has fallen by 18 days over the past 100 years. This ice provides habitat for species of diatom, which sink to the Lake bottom as the ice retreats, where their bodies provide critical nutrients for species living in the depths. Few places on Earth have experienced such changes in species composition and seasonal timing at the rate that Lake Baikal has.

Seasons: Winter, Spring, Summer, Fall

Sources: Hampton, SE et al. “Sixty years of environmental change in the world’s largest freshwater lake- lake Baikal, Siberia.” Global Change Biology: Accepted May 2008 and Gardner, Timothy. “Lake warming faster than air.” – news.com.au 1 May 2008. Accessed Online 2 May 2008 http://www.news.com.au/story/0,23599,23628417-2,00.html

Climate Fact: Ice Break-Up Dates and Bears

administrator — Wed, 08 Oct 2008 20:36:11 +0000

Polar bears, Earth’s largest land predator, are most common on annual sea ice that sits over shallow seas. This ice provides the bears with a platform from which they can hunt for food. In Canada’s Western Hudson Bay region, which is at the southernmost extent of the polar bear’s range, winter and spring are the best times to hunt, as that is when there is the most ice cover and spring is when the most seals are available. By the time late spring and summer arrive, the Hudson Bay is ice-free, and the bears are essentially stranded from their prey until the ice freezes-up again. The bears must live on their fat reserves during this period, which generally lasts about four months. The earlier the ice breaks up in the spring, the less time the bears have to build fat reserves to survive the hungry periods. Warmer temperatures in the region mean that the ice is now breaking up an average of three weeks earlier than it did 30 years ago, and a correlation exists between the date of the break-up and starvation induced mortality in young and older bears. Overall, the region’s Polar Bear population declined from 1194 in 1987 to 935 in 2004. While healthy adult bears can usually survive the extra stress of earlier ice break-up, years when ice breaks-up especially early generally correspond to more human-bear encounters, as the bears stray from their usual territories to find food.

Seasons: Spring, Summer

Source: Regehr, EV et al. “Effects of Earlier Sea Ice Breakup on Survival and Population Size of Polar Bears in Western Hudson Bay.” The Journal of Wildlife Management 71 (2007): 2673-2683.

Climate Fact: Spruce Beetle Surge

administrator — Wed, 08 Oct 2008 20:20:57 +0000

While forests fires may be the most visible and dramatic events that reshape North America’s forests, outbreaks of insect “pests” actually affect an area 45 times larger than that affected by fire. Generally, insects attack trees weakened by things like drought, wind storms, and fire, as healthy trees are usually able to fend-off attacks from pests. If the pests attack the tree in large enough numbers, however, the tree’s natural defenses can become overwhelmed. Spruce beetle populations become “outbreaks” when there is a large enough population of already weakened host trees (more than two clumps of five trees in a five acre area) and the right climatic conditions. In America’s Intermountain region, the right climate conditions for an outbreak include winter temperatures that do not drop below negative 29 degrees Fahrenheit (the temperature at which beetle larvae freeze to death), warmer fall temperatures (which allow the beetles to have more life cycles in a shorter period of time), and several years of drought (which weaken trees). Since 1976, there has been a 5.4 degree Fahrenheit increase in average wintertime temperatures and a 3.4 degree Fahrenheit increase in average autumn temperatures in the Intermountain Region. Also, the percentage of the western United States that is in drought condition has doubled over the past century.

Seasons: Winter, Spring, Summer, Fall

Sources: Logan, JA et al. “Assessing the impacts of global warming on forest pest dynamics.” Frontiers in Ecology and the Environment 1 (2003) 130-137 and Hebertson, EG and Jenkins, MJ. “Climate Factors Associated with Historic Spruce Beetle (Coleoptera: Curculionidae) Outbreaks in Utah and Colorado.” Environmental Entomology 37 (2008) 281-292 and “U.S. Temperature and Precipitation Trends.” U.S. National Oceanic and Atmospheric Administration (NOAA): Climate Prediction Center. 5 January 2005. 26 June 2008 < http://www.cpc.ncep.noaa.gov/charts.shtml> and United States. Climate Change Science Program. Weather and Climate Extremes in a Changing Climate. Synthesis Assessment Product 3.3: GPO. 2008.

Climate Fact: Forest-Tundra Dynamics

administrator — Wed, 08 Oct 2008 20:14:10 +0000

In northern Québec, patches of Black Spruce forests exist alongside the arctic shrub tundra, forming an ecological zone known as forest-tundra. Heavy winter snows, short frost-free growing seasons, and high winds limit the possible area in which Black Spruce trees can grow. These harsh conditions also limit how tall these trees can grow, and in the zones where climate conditions are just tolerable enough for the trees to survive, the spruces will grow in bushes as opposed to upright trees in order to limit their exposure to the elements. Since the 1980’s, when a twenty year regional cooling trend ended, spruce shrubs that had previously been limited by high wind and low temperatures have grown taller throughout the forest-tundra zone.

Seasons: Winter, Spring, Summer, Fall

Source: Gamache, Isabelle and Payette, Sergei. “Height growth response of tree line black spruce to recent climate warming across the forest-tundra of eastern Canada.” Journal of Ecology 92 (2004): 835-845.

Climate Fact: Rwenzori Mountain Glaciers

administrator — Wed, 08 Oct 2008 20:07:19 +0000

Temperatures in the East African Highlands have risen by about one degree Fahrenheit over the past 50 years. This area includes Uganda’s Rwenzori Mountains, which feature glaciers that supply the lowland plains region with water. Between 1987 and 2003, the area covered by glaciers in these mountains shrunk by about 50 percent. This retreat has been attributed to the temperature rise, a reduction in snowfall, and a decrease in average cloud cover, which has encouraged increased sublimation, or the conversion of a solid (in this case ice) to gas (in this case water vapor).

Seasons: Spring, Summer, Fall

Source: The United Nations: Environment Programme. Africa: Atlas of our Changing Environment. Malta: ProgressPress Inc., 2008. Accessed Online 11 June 2008 <http://www.unep.org/dewa/africa/AfricaAtlas/PDF/en/Africa_Atlas_Full_en.pdf>

Climate Fact: Copepod Range Change

administrator — Wed, 08 Oct 2008 17:28:24 +0000

The Labrador Sea Water (LWS) is a stream of cold, fresh, and oxygen rich water that travels down the western Atlantic coast from the Labrador Sea, which is located between Greenland and Newfoundland, towards the Equator. This stream forms in the late fall/early winter after the seasonal accumulation of glacial melt water, which is less dense than salt water, has pooled on the surface. As the strong northwesterly winter winds start to blow across the Labrador Sea, the fresh water pool cools, sinks to a depth of about 5,000 feet, and travels down the East Coast of Canada. The North Atlantic Oscillation (NAO), or the cyclical change in the pressure difference between the Azores High and Icelandic Low, controls the strength of these winds. During positive NAO phases (when the Azores High is particularly high and the Icelandic Low is particularly low), the winds are stronger, which leads to more cooling on the surface and a stronger flow of the Labrador Sea Water. The stronger the flow of this water, the cooler the waters along America’s east coast are. Over the last 30 years, the NAO was strongly and predominately positive, and copepod species (small crustaceans that collectively constitute the biggest source of protein in the oceans) that were previously found only in the waters off Canada, began showing up as far south as New Jersey, and increased in abundance all along the New England coast.

Seasons: Fall, Winter

Source: Johns, DG. “Arctic boreal plankton species in the Northwest Atlantic.” Canadian Journal of Fisheries and Aquatic Sciences 58 (2001): 2121-2124.

Climate Fact: Warming and Water Discharge

administrator — Wed, 08 Oct 2008 17:23:02 +0000

The Arctic Ocean is surrounded by a series of river drainage basins, which collectively occupy an area 1.5 times that of the ocean basin itself. No other ocean basin’s temperature and salinity levels are more dependent on what happens on the adjacent land surface. These temperature and salinity levels in turn influence the behavior of the world’s ocean conveyor system, which transports heat and nutrients to and from different ocean basins. The Eurasian Arctic has warmed by about 1.3 degrees Fahrenheit since the 1930’s. As this has happened, the total combined annual discharge of the six largest Eurasian rivers that flow into the Arctic Ocean has grown by 34 trillion gallons, or seven percent. These trends have corresponded to increases in winter precipitation and thawing permafrost. Total discharge also appears to be related to the behavior of the North Atlantic Oscillation (NAO), or the cyclical change in the pressure difference between the Azores High and Icelandic Low. Positive phases bring more precipitation to Scandinavia and Siberia, and the NAO has been predominately and strongly positive over the last 30 years.

One of the six rivers studied is Russia’s Lena River. To see a colorful LANDSAT image of the Lena River Delta, visit http://earthasart.gsfc.nasa.gov/lena.html.

Seasons: Spring, Summer, Fall

Sources: Peterson, BJ et al. “Increasing River Discharge to the Arctic Ocean.” Science 298 (2002): 2171-2173 and Serreze, MC et al. “Large-scale hydro-climatology of the terrestrial Arctic drainage system.” Journal of Geophysical Research 108 (2003): doi:10.1029/2001JD000919 and McGuire, AD et al. “Land cover disturbance and feedbacks to the climate system in Canada and Alaska.” Chapter 9 (pages 139 - 161) in Imzd Change Science: Ohsel-virzg, Moniloritig, and Ulzder*stnditzg Trojectol-ies of Challge OH the Earth’s SU+KZE. ditcd by Gutman, C., Janetos, A.C., Justice, C.0, Moran, E.F., Mustard, J.F., Rindf~lssR, .R., Skole, D., Turner 11, B.L., and Cochrane, M.A. Dordrecht, Ncthcrlands, Kluwer Adademic Publishers.

Climate Fact: Expanding Larch Forests

administrator — Tue, 07 Oct 2008 20:19:57 +0000

Over the 20th century in the polar region of Russia’s Ural Mountains, there was a 1.6 degree Fahrenheit rise in average summertime temperature. Cold temperatures are usually the limiting factor for tree growth at the poles and high elevations. Warming tends to allow trees to grow at higher elevations than they previously could, and also allow trees that could only survive growing close to the ground like bushes to grow upright. As the Urals have warmed, Larch forests (Larches are deciduous conifers) have moved uphill by between 65 and 200 feet, with 87 percent of the trees growing in the recently colonized areas emerging after 1970, when most of the warming trend has taken place. Also in these forests, 36 percent of the trees over 100 years in age grow like bushes, while 90 percent of the trees that have emerged since 1950 grow upright.

Seasons: Spring, Summer, Fall

Source: Devi, Nadezhda et al. “Expanding forests and changing growth forms of Siberian larch at the Polar Urals treeline during the 20th century.” Global Change Biology 14 (2008): 1581-1591.

Climate Fact: California’s Castle Lake and Climate

administrator — Tue, 05 Aug 2008 15:18:51 +0000

During the last ice age, an advancing glacier carved out a basin in the Siskiyou Mountains of what is northern California today. As the glacier melted, Castle Lake was formed. Every spring, as the ice on the lake melts and warm water on the bottom of the lake moves to the surface, stirring up nutrients in the process, blue-green algae and single celled organisms called diatoms bloom. These organisms ultimately feed the rest of the life in the lake, and are thus called the lake’s ”primary producers.” The earlier the ice melts, the warmer the lake’s water is during the summer, and the more primary production there is. Water temperature during the summer is regulated by the El Nino Southern Oscillation (ENSO) cycle. During summers that follow strong El NiÃ±o events (such as the summers of 1983 and 1998) water temperature and primary production are generally lower than average. Additionally, the area around Castle Lake has experienced a warming of 1.6 degrees Fahrenheit over the past 50 years, and during this same period in California and Nevada, the date when mountain snowpack melts has advanced an average of 19 days earlier in the year. All of these trends favor earlier ice-melt dates.

Season: Winter, Spring, Summer, Fall

Source: Park, S et al. “Climatic forcing and primary productivity in a subalpine lake: Interannual variability as a natural experiment.” Limnology and Oceanography 49 (2004): 614-619.

Climate Fact: Mistiming in the Mountains

administrator — Tue, 15 Apr 2008 20:26:58 +0000

In the Rocky Mountains, when plants produce their flowers and how many flowers these plants produce is dependent upon the depth of snow pack and when it melts. Snowpack actually protects the plants that are waiting underneath from early spring frosts, which can damage the plants’ emerging flowers. Generally, flowers come out when snow melts and bare ground appears. In contrast to other parts of the West, in the Four Corners States, increases in winter precipitation over the last 50 years have resulted in more snowpack, with El Niño years corresponding to above average fall and spring precipitation and La Niña years (such as this year) corresponding to below average fall and spring precipitation. Although the average November through March temperatures in these states have risen along with the rest of the West, the average date when there ceases to be snow on the ground is now coming an average of nine days later in the year, simply because there is now much more snow to melt. Because the temperature is warmer, however, migratory species like the Robin are arriving and hibernating species like the Marmot are waking earlier in the year. Unfortunately for these species, the delay in the appearance of bare ground means that their food sources are often not ready for their arrival.

Seasons: Spring, Summer

Sources: Inouye, DW et al. “Climate change is affecting altitudinal migrants and hibernating species.” Proceedings of the National Academy of Sciences 97 (2000): 1630-1633 and Mote, PW et al. “Declining mountain snowpack in western North America.” Bulletin of the American Meteorological Society 86 (2005): 39-49 and Groisman, PY et al. “Heavy precipitation and high streamflow in the United States: Trends in the 20th Century.” Bulletin of the American Meteorological Society 82 (2001): 219-246 and Inouye, DW et al. “Variation in timing and abundance of flowering by Delphinium barbeyi Huth (Ranunculaceae): the roles of snowpack, frost, and La Niña, in the context of climate change.” Oecologia 130 (2002): 543-550.

Climate Fact: Soil Frost Trends (Indianapolis, IN)

administrator — Tue, 15 Apr 2008 20:04:43 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter before the freeze has penetrated the soil, the soil freeze will generally not be as deep. For the same reason, if the ground is in a deep freeze when the snow falls, the duration of the freeze will generally be longer. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate at least a 15 percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Indianapolis area. During the early part of the 20^th Century, the soils around Indianapolis would stay frozen for an average of 52 days a year, whereas they now stays frozen for an average of 44 days a year.

Season: Spring

Source: Sinha, Tushar, et al. Agricultural and Biological Engineering Department, Purdue University. “Historic climate change impacts on soil frost in the Mid-Western United States.” 88^th Annual Meeting of the American Meteorological Society. New Orleans, LA. 21 January 2008.

Climate Fact: Soil Frost Trends (Detroit, MI)

administrator — Tue, 15 Apr 2008 20:02:02 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter before the freeze has penetrated the soil, the soil freeze will generally not be as deep. For the same reason, if the ground is in a deep freeze when the snow falls, the duration of the freeze will generally be longer. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate at least a 15 percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Detroit area. During the early part of the 20^th Century, the soils around Detroit would stay frozen for an average of 93 days a year, whereas they now stay frozen for an average of 71 days a year.

Season: Spring

Climate Fact: Soil Frost Trends (Chicago, IL)

administrator — Tue, 15 Apr 2008 20:00:19 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter, the soil freeze will generally not penetrate as deep as it would if the snow were absent even if the air temperature gets extremely cold. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. In Madison, WI, for example, large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes indicate about a three percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Madison area. During the early part of the 20^th Century, the soils around Madison would stay frozen for an average of 111 days a year, whereas they now stay frozen for an average of 108 days a year. Over the same period in the South Bend area, there has been a 15 percent decrease in the number of regional soil frost days, and while the soils there would stay frozen for an average of 73 days in the early 20^th Century, they now stay frozen for an average of 54 days.? ? ?

Season: Spring

Climate Fact: Soil Frost Trends (Minneapolis - St. Paul, MN)

administrator — Tue, 15 Apr 2008 19:57:59 +0000

During the winter in the northern Midwest, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter before the freeze has penetrated the soil, the soil freeze will generally not be as deep. For the same reason, if the ground is in a deep freeze when the snow falls, the duration of the freeze will generally be longer. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Midwest are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate at least a seven percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Minneapolis area. During the early part of the 20^th Century, the soils around Minneapolis would stay frozen for an average of 121 days a year, whereas they now stay frozen for an average of 112 days a year.

Season: Spring

Climate Fact: Heavy Rainfall Events

administrator — Tue, 15 Apr 2008 19:55:53 +0000

Since 1910, overall precipitation in the lower 48 states has increased by ten percent. This extra ten percent has made heavy and extreme precipitation events more frequent and more intense. Extreme precipitation events are defined as a 24-hour period with more than two inches of rainfall, and over the last century the proportion of rainfall events that fall in this category has risen from nine percent to eleven percent. In the Northeastern and Southeastern Regions, heavy rainfall events are closely correlated with high stream flow events during the months of maximum streamflow. In other words, in these Regions, above average streamflow events are now more likely to occur during seasons when the streamflow volume is already high.

Season: Spring

Sources: Trenberth, Kevin et al. Effects of Changing Climate on Weather and Human Activities. Sausalito, CA : 2000. University Corporation for Atmospheric Research and National Weather Service: Climate Prediction Center. U.S. Temperature and Precipitation Trends: Annual. Accessed Online 3 July 2007 http://www.cpc.noaa.gov/anltrend.gi and Groisman, PY et al. (2001). “Heavy Precipitation and High Streamflow in the Contiguous United States: Trends in the Twentieth Century.” BAMS, Vol. 82, No. 2.

Climate Fact: Soil Frost Trends (South Bend, IN)

administrator — Tue, 15 Apr 2008 19:47:52 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter before the freeze has penetrated the soil, the soil freeze will generally not be as deep. For the same reason, if the ground is in a deep freeze when the snow falls, the duration of the freeze will generally be longer. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate at least a 15 percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the South Bend area. During the early part of the Twentieth Century, the soils around South Bend area would stay frozen for an average of 73 days a year, whereas they now stay frozen for an average of 54 days a year.? ? ? ?

Season: Spring

Climate Fact: Soil Frost Trends (Lansing-Jackson, MI)

administrator — Tue, 15 Apr 2008 19:45:07 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter before the freeze has penetrated the soil, the soil freeze will generally not be as deep. For the same reason, if the ground is in a deep freeze when the snow falls, the duration of the freeze will generally be longer. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate at least a 15 percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Lansing area. During the early part of the Twentieth Century, the soils around Lansing would stay frozen for an average of 105 days a year, whereas they now stay frozen for an average of 90 days a year.

Season: Spring

Climate Fact: Soil Frost Trends (Wisconsin)

administrator — Tue, 15 Apr 2008 19:41:00 +0000

During the winter in the northern Mid-West, the uppermost ten centimeters of the soil surface freezes. The duration and the depth of the soil freeze are dependent upon the severity of the winter. Warmer winters mean shallower and shorter-lived soil freezes, whereas colder winters mean deeper and longer-lived soil freezes. Also, because snow acts as an insulator, if it snows early in the winter, the soil freeze will generally not penetrate as deep as it would if the snow were absent even if the air temperature gets extremely cold. Soil freeze properties have implications for spring stream flow, soil erosion, and soil cohesion and strength, all of which affect wildlife, agriculture, and water supply and quality. Winters in the Great Lakes Region are now warmer than they were in the early years of the 20^th Century, and the frost-free period, or the time between the last frost in spring and the first frost in fall, is up to two weeks longer. Large scale water cycle models that were calibrated to observed trends in soil temperature and stream flow volumes, indicate about a three percent decline in the number of regional soil frost days, and an increase in the winter soil temperature at most sites in the Madison area. During the early part of the Twentieth Century, the soils around Madison would stay frozen for an average of 111 days a year, whereas they now stay frozen for an average of 108 days a year.

Season: Spring?

Source: Source: Sinha, Tushar, et al. Agricultural and Biological Engineering Department, Purdue University. “Historic climate change impacts on soil frost in the Mid-Western United States.” 88^th Annual Meeting of the American Meteorological Society. New Orleans, LA. 21 January 2008.