Earth Gauge » Seasonal Patterns

Climate Fact: Japan Bloom Dates

administrator — Wed, 08 Oct 2008 21:44:16 +0000

Since 1953, the dates when Japan’s plants bloom in the spring have been arriving progressively earlier in the calendar year, and the dates when the trees change color and lose their leaves in the fall have been arriving progressively later. The average date when the country’s famous Cherry trees bloom is now arriving an average of 4.2 days earlier in the year, while Apricot trees are blooming an average of 5.4 days earlier, Camellias an average of 9.4 days earlier, and Dandelions an average of six days earlier. These trends correspond to increases in average spring temperatures. Additionally, the trends are most pronounced for plants growing in Japan’s big cities, which highlights how the Urban Heat Island Effect, or the tendency for cities to be warmer than surrounding rural areas, affects plant life. During the fall, the trends are essentially the opposite. Compared to the 1950’s, the leaves on Ginkgo and Japanese Maple trees are changing color an average of 10.7 and 15.4 days later in the year, respectively.

Season: Spring

Source: Japan Meteorological Agency (2007). “Long-term trends of phonological events in Japan: Summary of ‘Report on Climate Change 2005.’” Accessed Online 18 April 2008 ds.data.jma.go.jp/tcc/tcc/news/PhenologicalEventsJapan.pdf

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: Mid-latitude Moths and Mating

administrator — Wed, 08 Oct 2008 20:05:10 +0000

In the mid-latitude climates, insect species have a dormant period during the cold winter months, meaning that there is a limited period of time throughout the year when they can reproduce. In regions where there is little seasonal difference in rainfall and temperature, such as in the equatorial rainforests, insects do not have a dormant period and most species produce multiple generations each year. For many (but not all) mid-latitude insect species, the number of generations a species will have each year is dependent upon the temperature, especially in the spring. The earlier in the year the temperature stops dropping below freezing (the beginning of the frost-free period or growing season), the earlier in the year insects can lay eggs that are likely to survive until they hatch, and the more generations they can have. The grape berry moth, a native of eastern North America, is one species that makes use of warm springs to have more generations of offspring. In years when the cumulative average temperature is below 61 degrees Fahrenheit, most individual grape berry moths will have two generations. In years when the temperature exceeds 61 degrees, however, many individuals within the species will have three generations.

Seasons: Spring, Summer

Source: Tobin, PC et al. “Historical and projected interactions between climate change and insect voltinism in a multivoltine species.” Global Change Biology 14 (2008): 951-957.

Climate Fact: Rainfall Declines in Southeast Australia

administrator — Wed, 08 Oct 2008 19:43:43 +0000

Autumn (March to May) rainfall in southeast Australia is important for soil moisture and river recharge because the region is dependent on reliable water sources for cereal crop production. Since 1950, there has been a 40 percent decline in the region’s average autumn rainfall. This has been linked to fewer occurrences of La Niña events, more El Niño events, and a change in the “pressure wave-train” circulation pattern that brings rainfall from the sub-tropical Indian Ocean to southeast Australia. The increased frequency of El Niño events and the change in the wave-train circulation pattern, as well as a rise in atmospheric pressure over the region, have been linked to rising sea-surface temperatures in the Pacific and Indian Oceans. The last two autumns have seen record low inflows into the Murray River, an important source of water for the region’s farmers.

Seasons: Spring, Summer

Sources: Commonwealth Scientific and Industrial Research Organisation (CSIRO): Media Center. “Understanding autumn rain decline in SE Australia.” 23 May 2008. Accessed Online 9 June 2008 <http://www.csiro.au/news/UnderstandingDeclineAutumnRain.html> and Wahlquist, Asa. “Dry future well ahead of schedule.” The Australian, 7 June 2008. Accessed Online 9 June 2008 <http://www.theaustralian.news.com.au/story/0,25197,23822411-11949,00.html>

Climate Fact: Chinook Survival

administrator — Wed, 08 Oct 2008 19:34:02 +0000

Did you know that 75 percent of the water resources in the West originate from snowmelt? Mountain snowpack accumulates over the winter and as it melts during the spring, summer, and fall, it feeds the region’s rivers and streams. Over the last half of the 20th Century, November to March temperatures in the Pacific Northwest rose by about 4.5 degrees Fahrenheit. This trend has corresponded to less snowpack, an earlier melting of snowpack, and more late winter and early spring precipitation falling as rain instead of snow. Between 1950 and 1998, the average date when there ceased to be snow on the ground advanced 16 days earlier in the year, and the point in the year when river levels peak is now arriving an average of nine days earlier than it did in the 1950’s. This trend in earlier peak flow also means that average autumn stream levels are lower than they were 50 years ago, and that the water in these streams is warmer. Salmon are cold water species, and cannot tolerate significant rises in temperature. Low stream levels impede their ability to navigate the waters, and also generally mean poor water quality. The high-elevation streams in Idaho’s Salmon River watershed host populations of juvenile Chinook salmon, which remain in these streams for a year before venturing into larger water bodies. Fall stream flow is the most important climatic factor for estimating juvenile survival rates, which largely control Pacific Chinook salmon populations.

Seasons: Summer, Fall

Sources: “HydroFacts.” Southwest Journal of Hydrology 6 (2007): 13 and Mote, P.W., A.F. Hamlet, M.P. Clark, and D.P. Lettenmaier. 2005. Declining mountain snowpack in western North America. Bull. Amer. Met. Soc. 86:39–49 and Groisman, P.Y., P.W. Knight, and T.R. Karl. 2001. Heavy precipitation and high streamflow in the United States: Trends in the 20th Century. Bulletin of the American Meteorological Society 82:219-246 and Crozier, L. and Zabel, R.W. “Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon.” Journal of Animal Ecology 75 (2006): 1100-1109.

Climate Fact: Maritime Influences on Mountain Hemlock

administrator — Wed, 08 Oct 2008 18:25:55 +0000

In the Pacific Northwest, Mountain Hemlocks grow at elevations between 3,600 and 7,500 feet. These shade tolerant trees grow underneath the faster growing but shorter-lived Douglas Firs, and gradually make their way to the top of the canopy over their 700 year life spans. At the region’s high elevations, some of the world’s most extensive seasonal snowpack forms. The extent of this snowpack and its seasonal duration determine how much Mountain Hemlocks can grow each year. Warmer years (years when more precipitation falls as rain instead of snow, and the accumulated snow pack melts earlier in the spring) tend to be years of enhanced tree growth in the northern portion of the Hemlock’s range, and wider tree rings correspond to those years. In the southern extent of the Hemlock’s range (southern Oregon), however, the climate is different and warm temperatures and lack of snowpack limit hemlock growth. Here, the growth trends are essentially the opposite seen in the more northern areas of the species’ range. The Pacific Decadal Oscillation (PDO), a 50-year cycle of sea-surface temperature shifts in the northern Pacific, seems to largely control the depth and duration of Pacific Northwest snowpack. Positive (warm) phases of the PDO, which occurred between about 1920 until about 1945, and from about 1977 until just a few years ago, correspond to warmer temperatures in the Pacific Northwest and less snowpack.

Seasons: Winter, Spring, Summer, Fall

Source: Peterson, DW and Peterson, DL. “Mountain Hemlock Growth Responds to Climatic Variability at Annual and Decadal Time Scales.” Ecology 82 (2001): 3330-3345.

Climate Fact: White Spruces Withering

administrator — Wed, 08 Oct 2008 17:51:47 +0000

While cold temperatures limit growth for many plant species inhabiting the boreal forest and tundra regions of the northern hemisphere (from about 50 to 80 degrees North), increases in temperature can cause more evaporation from the soil and lead to drought stress. This appears to be the case with White Spruce forests in Alaska. A longer growing (or frost free) season and an increase in average May through August temperatures of six degrees Fahrenheit over the last 100 years have corresponded to decreases in annual growth rates. Large annual tree rings grew during the cool and wet period of 1915 to 1965. Since then, however, there has been a 40 to 50 percent decline in average annual tree ring width. During the cool and wet 1930’s, it was not unusual for the White Spruce trees to grow two millimeter-wide tree rings (a little more than one 16th of an inch). Today, one millimeter rings are more common. Warmer temperatures appear to be causing the soil to dry earlier in the summer, and when this happens the trees stop growing and start preparing for winter.

Seasons: Spring, Summer

Source: Barber, V et al. “Reduced growth of Alaskan white spruce in the twentieth century from temperature-induced drought stress.” Nature 405 (2000): 668-673.

Climate Fact: Cotton Yields and Climate

administrator — Tue, 07 Oct 2008 20:09:02 +0000

A common cotton disease in the southeast, hardlock, is caused by fungus and affected by temperature and humidity. The disease does better during years when humidity and rainfall levels are above average, especially during the months of July to September, when cotton plant flowers and bolls (pods containing 32 seeds from which the cotton fibers grow) mature. During the wet and humid year of 2002 in Florida, hardlock caused crop yields to decrease from 650 pounds per acre to 400, or 20 million dollars in lost yield. Drier and less humid years, on the other hand, discourage fungal growth and favor high yields. Over 50 percent of the variability in yields in the southeastern U.S. can be explained by climate. Years with the highest cotton yields correspond to years with lower than normal sea surface temperatures (SSTs) in the Gulf of Mexico and Atlantic Ocean, where the winds that blow into the southeast during the summer originate. These lower SSTs mean less humidity, and cause relatively dense air to become concentrated in upper air masses, which discourages convective cloud formation and rainfall.

Seasons: Summer, Fall

Sources: Baigorria, GA et al. “Assessing Predictability of Cotton Yields in the Southeastern United States Based on Regional Atmospheric Circulation and Surface Temperatures.” Journal of Applied Meteorology and Climatology 47 (2008): 76-90 and The University of Florida Education and Research Center. “Cotton/Hardlock.” Accessed Online 1 October 2008 <http://nfrec.ifas.ufl.edu/cottonhardlock.htm> and Cotton’s Journey. “The Story of Cotton.” Accessed Online 1 October 2008 <http://www.cottonsjourney.com/storyofcotton/page3.asp>

Climate Fact: North Atlantic Seabird Success

administrator — Tue, 07 Oct 2008 19:51:53 +0000

Seabirds, such as auks, gulls, petrels, terns, and gannets, have spent tens of millions of years adapting to life on the ocean. Some species, such as the Sooty Tern, can spend years at sea before returning to land. The success of these species is dependent on the success of their food sources (such as fish and plankton), and the success of these food sources is dependent on oceanic conditions such as sea-surface temperatures and the behavior of ocean currents. In the North Atlantic, changes in the North Atlantic Oscillation (NAO), or the cyclical change in the pressure difference between the Azores High and Icelandic Low, affect ocean currents. A 30-year study of summertime seabird breeding success indicates that seabird species on both sides of the Atlantic have more offspring in years when the waters are warmer, and in years when the previous year’s winter featured a predominately negative NAO (a negative NOA means that the difference between the aforementioned pressure centers is lower and the westerly winds blowing across the ocean are not as strong). The North Atlantic Basin has experienced an overall warming trend over the last 50 years, although the sub-polar waters, where most of the breeding activity takes place, have actually cooled. Also during this period, the NAO has transitioned from being predominately negative to predominately positive.

Seasons: Winter, Spring, Summer, Fall

Source: Sandvik, H et al. “A latitudinal gradient in climate effects on seabird demography: results from interspecific analyses.” Global Change Biology 14 (2008): 703-713.

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: British Invasion

administrator — Tue, 15 Apr 2008 20:24:29 +0000

During the spring and summer, moths and butterflies from continental Europe make a 100-mile journey across the open sea to the south coast of England. Over the past three decades, the average number of butterfly and moth species that make the annual migration has increased at a rate of 1.34 species each year. This increase is closely linked to temperatures in Western Europe; on average, for every 1.8 degree Fahrenheit rise in temperature there, an additional 14 species make the journey. Additionally, as temperatures in England have risen, the Spotted Wood Butterfly has moved north into Scotland, where temperatures are now closer to the species’ preferred range. This butterfly had not been seen in Scotland for 200 years.

Season: Spring

Sources: Sparks, T et al. “Increased migration of Lepidoptera linked to climate change.” European Journal of Entomology 104 (2007): 139-143 and Wheldon, Julie. “Forget the four seasons… soon there could be only two.” Daily Mail 2 February 2007. Accessed Online 14 February 2007,? www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_id=433226&in_page_id=1770&in_a_source=>)

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.