Mahsa Icefield Retreat and Separation, Baranof Island, Alaska

The Mahsa Icefield is at the headwaters of Takatz Creek.  This is a small glacier, not an actual icefield.  Five kilometers to the west is another small unnamed glacier at the headwaters of Sawmill Creek.  Here we focus on changes in the two glacier using Landsat images from 1986 to 2014.mahsa icefield ge

Google Earth image

In 1986 the Mahsa Icefield is a contiguous glacier that extended 5 km from east to west, red arrow indicates  the mid-section of the icefield.  A separate glacier in Sawmill Creek, yellow arrows, was 2.1 km long and has no lake at its terminus.  In 1997 the Mahsa Icefield has separated into an east and west half, at the red arrow, and has lost all of its snowcover.  The glacier in Sawmill Creek is still a single ice mass, but has lost all of its snowcover, which happened in 1998, 2003 and 2004. In 2014 the Mahsa Icefield’s east and west half are separated by 300 m, red arrow.  There is very little snowcover remaining despite there is a month left in the melt season.  At the headwaters of Sawmill Creek a lake has formed as the glacier has retreated, the lake is 600 m long in 2014.  The glacier has also separated into a small upper and lower section.  This glacier has lost half of its area since 1986.  The retreat of these glaciers on Baranof Island is similar to the retreat of nearby Carbon Lake Glacier,Lemon Creek Glacier, and Sinclair Glacier. Lemon Creek Glacier has lost more than 25 m of glacier thickness during the 1953-2014 period when its mass balance has been observed by the Juneau Icefield Research Program, and has retreated more than 1 km (Pelto et al, 2014).

mahsa icefield 1986

Landsat image 1986

mahsa icefield 1997

Landsat Image 1997

mahsa icefield 2014

Landsat image 2014

 

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Carbon Lake Glacier Retreat, Alaska

On Baranof Island in southeast Alaska there are a pair of unnamed glaciers at the headwaters of the Carbon Lake watershed, that then drains into Chatham Strait.  Here we examine changes in these glacier from 1986 to 2014 using Landsat imagery.  The blue arrow indicates the northern glacier terminus and the yellow arrow the southern glacier terminus region.

carbon lake ge

In 1986 the southern glacier terminus, yellow arrow consisted of three main tributaries combining to form a low sloped terminus region.  The northern glacier had a single terminus.  By 1997 a lake has formed at the southern glacier, which now has two separate termini, the red arrow indicates a new terminus area and the pink arrow the eastern portion of this glacier.  The northern glacier, blue arrow, is retreating but still joined.  By 2014 the southern glacier has separated into three parts.  There is a terminus at the red arrow, this represents a 900 m retreat since 1986.  This portion of the glacier has further separated since 1997 into two parts.  The eastern glacier, pink arrow has retreated 700 m since 1986.  The new alpine lake is 600 m long.  The northern glacier, blue arrow, has separated into two main termini and the glacier has retreated 200 m.   The retreat of these glaciers paralells the observed losses of other smaller glacier in the region most notably Lemon Creek Glacier, which is a World Glacier Monitoring Service reference glacier, 30 km west on the edge of the Juneau Icefield.  Another nearby example is Sinclair Glacier.  Lemon Creek Glacier has lost more than 25 m of glacier thickness during the 1953-2014 period when its mass balance has been observed by the Juneau Icefield Research Program, and has retreated more than 1 km.

carbon lake 1986

1986 Landsat image Carbon Lake Glaciers

carbon lake 1997

1997 Landsat image Carbon Lake Glaciers

carbon lake 2014

2014 Landsat image of Carbon Glacier