12:04 II "v? [3' Data CommAW- Data Home 1 Math Top Emiroumeul Topil T_ mm 3 Download the Data Data Set #044 m Rainbow Glacier Excel File snout posltlon 0 Texl File . I . A '50 . O . Minilab File g 0 3 100 . 3 About the Data E . . 3 M E 7150 . .4: 3 7200 o n. . . _ . 0 Help With Using Data 250 l y 1985 1990 1995 2000 calendar year On to Top, 0 About the Data About glacier retreat Glaciers are masses of ice moving downhill or downslope by either owing as a solid andJor sliding along their base. Glaciers grow and shrink in size over time, much like your checking account; glaciers have budgets. Glaciers grow (lengthen, widen and thicken) under favorable conditions, either by increasing deposits (more snowfall, more snow avalanches, etc.), by decreasing withdrawals (less melting, less calving of icebergs, etc.), or both until a positive mass balance is achieved. Glaciers decrease in size (shrink or retreat) by decreasing deposits (less snowfall, etc.), increasing withdrawals (less melting, etc.), or both, until a negative mass balance is achieved. As an alpine or valley glacier shrinks in size, the end of the glacier is found farther and farther uphill; the glacier is said to retreat. Shrinking glaciers can have profound effects on man and the environment. In the Pacic Northwest of the US, glaciers are found at the heads of many major river systems in both the Cascade and Olympic Mountains. Melting of these glaciers provides water for streams and rivers, especially in the months of August, September and October, when streamows are low due to lack of precipitation (Washington gets very little rain in the summer), The smaller the glacier, the smaller the outow of meltwater, Low streamflows lead to reduced electricity generation at hydropower plants downstream from shrinking glaciers, And low streamows can also have profound impacts on salmon viability, especially for the early fall spawners. Data on the recent changes in length of the Rainbow Glacier on Volcano Baker in the North Cascades of Washington State are shown in the table and gure (Pelto, 2001, personal communication), The data Show the position of the snout (terminus) of the Rainbow Glacier as a function of time, compared with the 1985 position. The changes in position of the snout are essentially equivalent to changes in the total length of the glacier, as the head of the glacier does not change position signicantly. As can be seen, the Rainbow Glacier has shrunk almost monotonically over the last 15 years. The students can t a linear regression to these data to determine the typical rate of change, though they should rst change calendar years to more practical values, There's a missing year; can linear interpolation be used to estimate a reasonable value? The Rainbow Glacier was 3750 m long in 1950; assuming a constant rate, how much did the glacier retreat in the previous 35 years? When will the glacier be half its 1950 length? Why is the Rainbow Glacier retreating? Students will be quick to answer "melting", but should remember that decreasing deposits can have just as big an impact on their bank account as increasing withdrawals. Reference: Mauri Pelto, Nichols College, North Cascades Glacier Climate Project httpz/fwwwnichols.edu/departments/Glacier/ B seattlecentral.edu 12:04 II 6? C)' _.__,_,__ m_ .AM.-,_ o. _z_ r..- . \"*5 -e \"A\"... H we .._,_Hr_ -J n...\" .H \"Arc, __ C so..- and/or sliding along their base. Glaciers grow and shrink in size over time, much like your checking account; glaciers have budgets. Glaciers grow (lengthen, widen and thicken) under favorable conditions, either by increasing deposits (more snowfall, more snow avalanches, etc), by decreasing withdrawals (less melting, less calving of icebergs, etc), or both until a positive mass balance is achieved. Glaciers decrease in size (shrink or retreat) by decreasing deposits (less snowfall, etc), increasing withdrawals (less melting, etc), or both, until a negative mass balance is achieved. As an alpine or valley glacier shrinks in size, the end of the glacier is found farther and farther uphill; the glacier is said to retreat. Shrinking glaciers can have profound effects on man and the environment. In the Pacific Northwest of the US, glaciers are found at the heads of many major river systems in both the Cascade and Olympic Mountains. Melting of these glaciers provides water for streams and rivers, especially in the months of August, September and October, when streamows are low due to lack of precipitation (Washington gets very little rain in the summer). The smaller the glacier, the smaller the outow of meltwater. Low streamows lead to reduced electricity generation at hydropower plants downstream from shrinking glaciers. And low streamows can also have profound impacts on salmon viability, especially for the early fall spawners. Data on the recent changes in length of the Rainbow Glacier on Volcano Baker in the North Cascades of Washington State are shown in the table and gure (Pelto, 2001, personal communication). The data show the position of the snout (terminus) of the Rainbow Glacier as a function of time, compared with the 1985 position. The changes in position of the snout are essentially equivalent to changes in the total length of the glacier, as the head of the glacier does not change position signicantly. As can be seen, the Rainbow Glacier has shrunk almost monotonically over the last 15 years. The students can fit a linear regression to these data to determine the typical rate of change, though they should rst change calendar years to more practical values. There's a missing year; can linear interpolation be used to estimate a reasonable value? The Rainbow Glacier was 3750 m long in 1950; assuming a constant rate, how much did the glacier retreat in the previous 35 years? When will the glacier be half its 1950 length? Why is the Rainbow Glacier retreating? Students will be quick to answer "melting", but should remember that decreasing deposits can have just as big an impact on their bank account as increasing withdrawals. Reference: Mauri Pelto, Nichols College, North Cascades Glacier Climate Project http://www.nichols.edu/departments/Glacier/ Go to Top. 3 View the Data Rainbow Glacier shrinkage, North Cascades, WA data courtesy of Mauri Pelto, North Cascades Glacier Climate Project, Nichols College position of glacier's snout relative to 1985 position negative values = glacier retreats/shortens year position (meters) 1985 0 1986 11 1987 .22 1988 33 1989 .44 1990 55 1991 -60 1992 :15 1993 .96 1994 -116 1995 .137 1996 ~16] 1997 1998 .201 1999 241 2000 .246 Go to To]; E seattlecentra|.edu