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Glacier Info - Winthrop Glacier

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Winthrop Glacier
On the northern slope of Mount Rainier this glacier was named for Theodore Winthrop who traveled by the mountain in 1853 as the region's first "tourist." Winthrop popularized the northwest in his book The Canoe and The Saddle. He was born in Connecticut in 1828 and was killed in Virginia on June 10, 1861, early in the Civil War. (Reese, 2009)

STATISTICS AS OF 2015 (Beason, 2017):

Aerial Extent:
3.47 ± 0.17 square miles (8.98 ± 0.45 km2) (Rank: 2 of 29)

Debris Cover:
1.35 ± 0.08 square miles (3.49 ± 0.20 km2) (Rank: 1 of 29)

Highest Elevation (Head):
14,379 feet (4,383 m)

Lowest Elevation (Terminus):
4,840 feet (1,475 m)

Elevation Range:
9,539 feet (2,907 m)

Length:
4.99 miles (8.03 km)

Average Slope:
29°

Average Flow Direction (Flows towards):
North northeast (13°)

CHANGE IN EXTENT, 1896-2015 (Beason, 2017):
Units 1896 1913 1971 1994 2009 2015
Area, mi2 3.18 3.93 3.72 3.84 3.09 3.47
Area, km2 8.23 10.18 9.63 9.94 8.01 8.98

Area change between periods
1913 1971 1994 2009 2015
1896 0.75 mi2
(1.95 km2)
0.54 mi2
(1.40 km2)
0.66 mi2
(1.71 km2)
-0.08 mi2
(-0.22 km2)
0.29 mi2
(0.74 km2)
1913 -- -0.21 mi2
(-0.55 km2)
-0.09 mi2
(-0.24 km2)
-0.84 mi2
(-2.17 km2)
-0.47 mi2
(-1.21 km2)
1971 -- 0.12 mi2
(0.31 km2)
-0.62 mi2
(-1.62 km2)
-0.25 mi2
(-0.65 km2)
1994 -- -0.74 mi2
(-1.93 km2)
-0.37 mi2
(-0.97 km2)
2009 -- 0.37 mi2
(0.96 km2)

Percent change between periods
1913 1971 1994 2009 2015
1896 23.7 % 17.0 % 20.8 % -2.7 % 9.0 %
1913 -- -5.4 % -2.4 % -21.3 % -11.8 %
1971 -- 3.2 % -16.8 % -6.8 %
1994 -- -19.4 % -9.7 %
2009 -- 12.0 %

ESTIMATED CHANGE IN VOLUME, 1896-2015 (George and Beason, 2017):
PLEASE see important notes about this, below...
Units 1896 1913 1971 1981* 1994 2009 2015
Volume, mi3 0.2627 0.3248 0.3072 0.4123 0.3172 0.2557 0.2864
Volume, km3 1.0949 1.3540 1.2806 1.7187 1.3221 1.0657 1.1936
* = 1981 was the only year that glacial volumes have been measured. See note below.

Basal Shear Stress (τ): 3,212.05 lbs/ft2

Volume change between periods
1913 1971 1981 1994 2009 2015
1896 0.0622 mi3
(0.2591 km3)
0.0446 mi3
(0.1857 km3)
0.1496 mi3
(0.6237 km3)
0.0545 mi3
(0.2272 km3)
-0.0070 mi3
(-0.0292 km3)
0.0237 mi3
(0.0987 km3)
1913 -- -0.0176 mi3
(-0.0734 km3)
0.0875 mi3
(0.3646 km3)
-0.0076 mi3
(-0.0319 km3)
-0.0692 mi3
(-0.2883 km3)
-0.0385 mi3
(-0.1604 km3)
1971 -- 0.1051 mi3
(0.4380 km3)
0.0100 mi3
(0.0415 km3)
-0.0516 mi3
(-0.2149 km3)
-0.0209 mi3
(-0.0871 km3)
1981 -- -0.0951 mi3
(-0.3965 km3)
-0.1566 mi3
(-0.6529 km3)
-0.1260 mi3
(-0.5251 km3)
1994 -- -0.0615 mi3
(-0.2564 km3)
-0.0308 mi3
(-0.1286 km3)
2009 -- 0.0307 mi3
(0.1279 km3)

Percent change between periods
1913 1971 1981 1994 2009 2015
1896 23.7 % 17.0 % 57.0 % 20.8 % -2.7 % 9.0 %
1913 -- -5.4 % 26.9 % -2.4 % -21.3 % -11.8 %
1971 -- 34.2 % 3.2 % -16.8 % -6.8 %
1981 -- -23.1 % -38.0 % -30.6 %
1994 -- -19.4 % -9.7 %
2009 -- 12.0 %

With the exception of data in 1981, all values here are calculated estimates based on work by Driedger and Kennard (1986), which calculates glacier volumes with the following equations:

If Glacier Length (L) > 8,500 ft:


If Glacier Length (L) < 8,500 ft:


Basal shear stress (τ) is calculated as:


Where V is the calculated volume of the glacier (ft3), A is the calculated area of the glacier (ft2), ρ is the density of ice (1.779 slug/ft3), g is the acceleration of gravity (32.178 ft/s2), and α is the average slope of the glacier.

If you need a really good research project, recalculating the glacier volumes at Mount Rainier is the way to go!

NOTES:


Data References: Beason, 2017, George and Beason, 2017, Reese, 2009, and Driedger and Kennard, 1986