By Matt Beedle
For the past three years my dad, Jack Beedle, has made an annual journey to a spot on Thunder Mountain to photograph Mendenhall Glacier. It’s a good 2-hour climb up to this location; a significant effort for one shot (Thanks, Dad!). We first visited this location – overlooking the Mendenhall Valley of Juneau, Alaska – in 1993 when I was in high school. The first repeat photograph my dad took yielded this photo pair, which I find quite stunning, especially in that the perspective provides a unique view of volume change in addition to area/length change:
Mendenhall Glacier has continued to retreat since 2010, but as the time between images is is only a few years as opposed to the better part of two decades, the results are not nearly as striking. This is how the change of Mendenhall Glacier appears from this vantage point since 2010:
The retreat from 2010 to 2011 is apparent, but it’s difficult to make out much change in the past year from this distance. Within the next decade it’s likely that Mendenhall Glacier will retreat to a point where it is no longer in contact with Mendenhall Lake. When this happens the calving process – by which glaciers can lose large amounts of mass – will end, and the retreat of Mendenhall Glacier should slow. Are we nearing that point? Did retreat of Mendenhall Glacier slow this past year? To try to answer these questions I did a quick investigation with satellite imagery from 1993, 2010, 2011, and 2012.
In 1993 Mendenhall Glacier extended to Nugget Falls, where a popular trail ends today, and many people play in the sand where the ice stood not too long ago. Since then it has retreated dramatically, especially where in contact with the lake where calving results in the loss of a great deal of mass. Note that the retreat along the bedrock peninsula that juts out into the lake, where the glacier is grounded and there is no calving, is much less. To measure the rate of retreat since 1993 I took the average across the entire terminus, including the portion that calves into Mendenhall Lake and the portion that is grounded on the bedrock peninsula.
Before I tell you the numbers I need to post a little disclaimer. Landsat satellite imagery, with a resolution of 30 meters (the width of each pixel represents 30 meters on the ground), is far from ideal to determine annual glacier length change. My intent here is to get a rough estimate of change to lend some context to the repeat photography.
With that said, here’s (roughly) how fast Mendenhall Glacier has been receding since 1993 when my dad and I first hiked Thunder Mountain:
- 1993 – 2010: Total retreat of 538 meters (m), or 32 m per year
- 2010 – 2011: 56 m
- 2011 – 2012: 40 m
- 1993 – 2012: Total retreat of 660 meters (m), or 35 m per year
[NOTE: Values reported here are rounded to the nearest meter and thus total retreat does not jive with the annual rates.]
From these measurements it appears that recent retreat of Mendenhall Glacier (2010 – 2012) has been greater than the average rates since 1993. Although it’s not readily apparent from the repeat photographs, the retreat of Mendenhall Glacier has continued in 2012, and at what appears to be a rate that is a bit faster than the average since 1993.
I too visited this site on Thunder Mountain this past summer with the intent of getting a shot of me standing in the same place as in 1993. Unfortunately I didn’t have the right lens in my camera kit that day to get the same perspective that was captured in 1993. I hope to return to Thunder Mountain with my dad in the summer of 2013 to capture the ’20th anniversary’ shot of our initial journey to this spot.
Standing on Thunder Mountain, 1993 image in hand, enjoying the stunning view of Mendenhall Glacier, I was struck by the incredible magnitude of change. Not really saddened, but more in awe of the incredible dynamism of the natural world around us. I’m captivated by these rapidly changing, intensely beautiful masses of ice and snow, and hope that I can bring a bit of this experience to you through images and a bit of analysis.