|
Castle
Creek Glacier
Castle
Length Change Record Kwadacha
Glacier Repeat
Glacier Photos Publications
About Me
|
 |
INTRODUCTION:
Since
1959 Castle Creek Glacier has formed a continuous series of annual push
moraines. These moraines have allowed us to reconstruct the
longest continuous record of annual glacier recession for a North
American glacier (Beedle et al., 2009). Here we present a
short
introduction to annual push moraines, the Castle Creek Glacier record,
and provide references to previous work on annual push moraines.
WHAT IS AN ANNUAL PUSH MORAINE: Annual push moraines form at the terminus of some glaciers where a number of conditions exist. To form an annual push moraine a glacier must undergo a seasonal (winter) advance. During this short-lived advance (reaching a maximum at the beginning of the melt season) a glacier will push sediment up along its margin - if readily-deformable sediment is present. In the melt season (summer) a glacier will recede from this moraine. To form a continuous series of annual push moraines, summer recession must outpace the winter advance, as any net advance would destroy previously formed moraines. The distance from one moraine to the next (from one maximum winter extent to the next) is a measure of the annual recession of the glacier. If the moraines - and distances between them - can be reliably dated, then a record of glacier recession can be reconstructed. For further information on push moraines please see the review paper on push moraines by Bennett (2001) and detailed studies of annual push moraines found in Norway (Andersen and Sollid, 1971; Worsley, 1974), Iceland (Sharp, 1984: Boulton, 1986; Krüger, 1995; Bradwell, 2004), and Canada (Beedle et al., 2009). |
 |
 |
 |
 |
| DATING ANNUAL PUSH MORAINES: To date annual push moraines we used known terminus positions mapped from 10 aerial photos. Each photo was taken in late summer or early autumn - at a time near the end of the melt season. During the melt season the terminus recedes from the moraine formed the previous winter. The moraine immediately down-valley from the known terminus position is dated as being formed during the previous winter. The number of moraines between known terminus positions coincides with the years between images, confirming that the moraines were formed annually. |
 |
CASTLE
CREEK GLACIER RECESSION: Castle
Creek Glacier has receded every years since 1959. This
recession
(1959 to 2008)
totals 719 meters (open gray circles at left) with an average of over
14 meters per year. The record of recession for South Cascade Glacier, Washington, USA (red) is included here for comparison, and can be accessed from the World Glacier Monitoring Service. Annual glacier recession correlates most strongly with summer temperature. In other words, warmer summers result in greater recession. However, attributing annual recession to climate variability is complicated by glacier flow dynamics (which are different for each glacier!) - annual recession is also influenced by precipitation that accumulated on a glacier in past decades. For further information on the Castle Creek Glacier push moraines, length change record, and relations to climate variability please see Beedle et al. (2009). |
| Andersen,
J. L., and J.
L. Sollid (1971), Glacial chronology and glacial geomorphology in the
marginal zones of the glaciers, Midtdalsbreen and Nigardsbreen, south
Norway, Norw.
J. Geogr., 25,
1-38. Beedle, M. J., B. Menounos, B. H. Luckman, and R. Wheate (2009), Annual push moraines as climate proxy, Geophys, Res. Lett., 36, L20501, doi:10.1029/2009GL039533 Bennett, M. R. (2001), The morphology, structural evolution and significance of push moraines, Earth Sci. Rev., 53, 197-236, Boulton, G. S. (1986), Push-moraines and glacier contact fans in marine and terrestrial environments, Sedimentology, 33, 677-698. Bradwell, T. (2004), Annual moraines and summer temperatures at Lambatungnajõkull, Iceland, Arct. Alp. Res., 36, 502-508. Krüger, J. (1995), Origin, chronology and climatological significance of annual-moraine ridges at Myrdalsjõkull, Iceland, Holocene, 5, 420-427. Sharp, M. (1984), Annual moraine ridges at Skállafellsjõkull, south-east Iceland, J. Glaciol, 30, 82-93. Worsley, P. (1974), Recent "annual" moraine ridges at Austre Okstindbreen, Okstindan, north Norway, J. Glaciol., 13, 265-277. |
