Tag: Cordillera Darwin glacier melt

Darwin Glacier, Chile 1986-2020 Retreat Opens New Fjord Arm

On By mspeltoIn chile glacier melt, chile glacier retreat

Darwin Glacier in Landsat images from 1986 and 2020. Red arrow indicates 1986 terminus location, yellow arrow 2020 terminus location, purple dots the snowline.  Point 1,2 and 3 indicate the same specific location.

Darwin Glacier flows east from the main divide of the Cordillera Darwin entering the head of Fjord Parry. Here we examine changes illustrated by Landsat images from 1986-2020.   Melkonian et al (2013) note widespread thinning of four large glaciers in the Cordillera Darwin Range from 2000-2011; Ventisquero Grande, Marinelli, Darwin and Roncagli, while the Garibaldi Glacier increased in volume.  They note a maximum velocity of 9.6 m/day at Darwin Glacier and thinning of over 3 m/year during the 2000-2011 period, which emcompasses a period of rapid retreat noted below. Davies and Glasser (2012) note that during the 1870-2011 period the Cordillera Darwin area loss was most rapid from 1986 to 2001. Dussaillant et al (2019) note the mass loss for the central Cordillera Darwin at -0.4 to -0.6 m/year from 2000-2018.

In 1986 Darwin Glacier extended beyond the end of a southwest trending valley (Point 3) and had fully separated from the former tributary flowing eastward. Tributaries at Point 1 and 2 join the main glacier within a 2 km of the current terminus. The snowline is at 500 m. By 2000 the glacier had retreated into the southwest trending valley, with a peninsula emerging on the west side at point 3.  The snowline is at 500 m. By 2019 the glacier had retreated beyond the former tributaries at Point 1 and 2. The snowline in 2018 is at 750 m.  In 2020 the peninsula at Point 3 has greened up with new vegetation, the glacier has retreated 3100 m since 1986 exposing a new fjord arm. Point 2 is largely a glacier free valley bottom.  The snowline is at 800 m.  A further 1 km retreat will lead to another tributary separation much as has happened at Ventisquero Grande.

Darwin Glacier in Landsat images from 2000 and 2019. Red arrow indicates 1986 terminus location, yellow arrow 2020 terminus location, purple dots the snowline.  Point 1,2 and 3 indicate the same specific location.

GLIMS view of Darwin Glacier with 1986-2007 margins indicated (Bethan Davies delineated margins).  Flow arrows added.

Videla Glacier Retreat, Tierra del Fuego, Chile Generates New and Expanding Lakes

On By mspeltoIn chile glacier retreat

Videla Glacier, Chile in 1997 and 2018 Landsat images. Red dots mark the 1997 terminus locations, yellow dots the 2018 terminus position and purple dots the snowline. 

Videla Glacier is a land terminating glacier in the northwest portion of the Cordillera Darwin Icefield (CDI). The glacier has terminates in several expanding proglacial lakes each in front of a different tongue of the glacier. The glacier flows northwest from Cerro Ambience towards Fiordo Profundo.  Meier et al (2018) identified area change of Patagonia glaciers from 1870-2016 with a ~16% area loss of CDI, with more than half of the loss occurring since 1985. They also noted that CDI glaciers were retreating fastest between 1986 and 2005; afterwards the rate of retreat has decreased. The retreat has been largest on tidewater glaciers such as Marinelli Glacier and Ventisquero Grande Glacier.

In 1997 of Videla Glacier’s six main terminus lobes, five did not exhibit a proglacial lake, only the two northern most lobes ended in a proglacial lake.  The northwestern lobe terminates in a 800 m long calving front, the northeastern lobe in the same basin exhibits a small fringing proglacial lake on its northern margin. The snowline in 1997 is at 600 m.  In 2001 the proglacial lake has expanded at both the northwestern and northeastern lobe.  A second proglacial lake has developed at the next most northern lobe.  The snowline in 2001 is at 550 m.  By 2017 Videla Glacier terminates in five expanding proglacial lakes and the snowline is the highest observed at 650 m. In December 2018 the terminus change from 1997 is evident at each lobe.  The main terminus is the northernmost that has both a northwestern and northeastern terminus.  In a Digital Globe image below the green arrows indicate areas where the terminus is rifted indicating partial flotation.  By 2018 the rifted terminus tongue of the northwestern lobe has been lost.  This image also reveals at the orange arrows newly exposed bedrock. The retreat has been 1.1 km for the northeastern lobe, 1.2 km for the northwestern lobe, 0.9 km for the next lobe to the south, and 0.7 km for the southern lobe. The initiation of significant retreat from the Little Ice Age maximum which led to moraine development impounding the most northern and southern proglacial lakes, was slow in this area. There has been more retreat since 1997 than since 1870.

Videla Glacier in 2001 Landsat image indicating proglacial lakes and the snowline.

Videla Glacier in 2017 Landsat image indicating proglacial lakes and the snowline.

 

Videla Glacier in a Digital Globe image indicating upglacier limit of weak rifted areas of the northeastern and northwestern lobe, green arrows.  Orange arrows indicate newly exposed bedrock.

 

Ventisquero Grande Glacier, Chile Retreats; Not so Grande in 2017

On By mspeltoIn chile glacier retreat

Ventisquero Grande Glacier comparison in Landsat images from 1997 and 2017.  Red arrows mark the 1997 terminus, yellow arrows the 2017 terminus, purple dots the snowline and purple arrow the junction of the tributaries. 

Ventisquero Grande Glacier is at the head of Ventisquero Seno in the Cordillera Darwin of Tierra del Fuego.  The fjord is just west of Garibladi Fjord and opens into Darwin Channel.  Melkonian et al (2013) note widespread thinning of four large glaciers in the Cordillera Darwin Range from 2000-2011; Ventisquero Grande (CDI-08), Marinelli, Darwin and Roncagli, while the Garibaldi Glacier increased in volume.  Here we examine changes in the glacier using Landsat and Sentinel Images from 1997 to 2017.

In 1997 two tributaries merged 3.2 km upglacier of the terminus, purple arrow, terminating in a 1.8 km wide calving front, red arrows.  In 1999 there is limited retreat and the calving front has extended to 2 km in length.  The transient snowline is at 700 m in 1997 and at 550 m in 1999, purple dots.  By 2002 the southern end of the terminus has retreated exposing a shoal.  By 2017 the  two tributaries have separated, purple arrow.  Retreat of the glacier has been 2100 m on the north side, 2800 m in the center and 2000 m on the south side. Both of the termini are still calving and extensive crevassing immediately upglacier of the terminus indicates significant glacier velocities.  The calving front is 2.1 km wide in 2017.  As Simon Gascoin has noted the addition of Sentinel imagery has helped expand the potential for images that are relatively cloud free. Melkonian et al (2013) note velocities of less than 2 m/day until right near the terminus. The transient snowline in 2017 is at 800 m on March 28, 2017. 

Ventisquero Grande Glacier comparison in Landsat image from 1999 and Sentinel 2 image from 2017.  Red arrows mark the 1997 terminus, yellow arrows the 2017 terminus, purple dots the snowline and purple arrow the junction of the tributaries. 

Ventisquero Grande Glacier  in 2002 Landsat image. Red arrows mark the 1997 terminus, yellow arrows the 2017 terminus, purple dots the snowline and purple arrow the junction of the tributaries. 

 

Ventisquero Grande Glacier in Sentinel 2 image from 2017.  Red arrows mark the 1997 terminus, yellow arrows the 2017 terminus,  and purple arrow the junction of the tributaries.