Bernardo glacier retreat – From a Glaciers Perspective

Bernardo Glacier in Landsat images from 1986 and 2021 illustrating retreat at the southern (S), middle (M) and northern (N) terminus respectively. Red arrows are 1986 terminus locations, yellow arrows are 2021 terminus locations. Separation from Tempano occurs at S, while lake expansion occurs at M and N.

Bernardo Glacier is an outlet glacier on the west side of the Southern Patagonia Icefield (SPI) that currently ends in an expanding proglacial lake system, with three primary termini. Here we examine changes from 1986 to 2021 using Landsat images. Davies and Glasser (2012) indicate that over the last century the most rapid retreat was from 2000 to 2011. Willis et a (2012) note a thinning rate of 3.4 meters per year during this period of the Bernardo Glacier region, which drives the retreat. Mouginot and Rignot (2014) illustrate that velocity remains above 200 m/year from the terminus to the accumulation zone on Bernardo Glacier. Eñaut Izagirre visited the glacier in 2019 and provided images of the middle terminus of Bernardo Glacier, below.

Bernardo Glacier in Landsat images from 1998 and 2020 illustrating retreat at the southern (S), middle (M) and northern (N) terminus respectively. Red arrows are 1986 terminus locations, yellow arrows are 2021 terminus locations. Separation from Tempano occurs at S, while lake expansion occurs at M and N.

In 1986 Bernardo the southern terminus of the glacier was in tenuous contact with Tempano Glacier. The middle terminus primarily ended on an outwash plain with a fringing proglacial lake developing. The northern terminus had retreated a short distance south from a peninsula that had acted as a pinning point. By 1998 the northern terminus had retreated into the wider,deeper portion of the lake basin that was now filled with icebergs. The middle terminus remained grounded on an outwash plain, with proglacial lake expansion at the NW corner of the terminus. A small lake has developed completely separating Bernardo Glacier and Tempano Glacier. By 2003 the northern terminus had retreated 2 km from 1986, the middle terminus 1.5 km and the southern terminus 1.2 km in an expanding proglacial lake. By 2015 the lake between Tempano and Bernardo Glacier had drained, but a fringing proglacial lake at the margin of Bernardo Glacier was forming. In 2015 the northern terminus had retreated 3.5 km since 1986, the middle terminus 2.5 km and the southern terminus 2.75 km. From 2015 to 2020 the change of the southern terminus was limited to a limited expansion of the fringing proglacial lake, a limited retreat of the the northern terminus, while the middle terminus had retreated significantly into a wider portion of the lake basin. By 2021 the southern terminus had retreated 3 km since 1986, the middle terminus 4.6 km and the norther terminus 4.1 km. This led to a 8.7 km2 lake expansion at the middle terminus and a 7.8 km2 lake expansion at the northern terminus. Gourlet et al (2016) identify Bernardo Glacier as having thinner ice than other large outlet glaciers such Jorge Montt or O’Higgins, which helps lead to rapid terminus change. The retreat is similar to the extensive retreat observed at Dickson Glacier and Upsala Glacier.

Southern Andean huemel an endemic deer on the foreland beyond Bernardo Glacier (photograph from Eñaut Izagirre).

Middle terminus of Bernardo Glacier in 2019 taken by Eñaut Izagirre who considers this a condor-view.

Bernardo Glacier in Landsat images from 2003 and 2015 illustrating retreat at the southern (S), middle (M) and northern (N) terminus respectively. Lake expansion and then drainage occurs at S. Red arrows are 1986 terminus locations, yellow arrows are 2021 terminus locations.

Comparison of 1986 and 2015 Landsat image of Bernardo Glaciers three termini, north, main and south. Red arrows indicate 1986 terminus location and yellow arrows the 2016 terminus location. Indicating the substantial retreat of each terminus and lake expansion for the north and main terminus, while the lake drained at the southern terminus.

Bernardo Glacier is a difficult to reach outlet glacier on the west side of the Southern Patagonia Icefield (SPI). It The glacier currently ends in an expanding proglacial lake system, with three primary termini. Here we examine changes from 1986 to 2016 using Landsat images. Willis et a (2012) quantify a rapid volume loss of the SPI from 2000-2012 of 20 giga tons per year mainly from rapid retreat of outlet glaciers. They note a thinning rate of 3.4 meters per year during this period of the Bernardo Glacier region. Mouginot and Rignot (2014) illustrate that velocity remains high from the terminus to the accumulation zone on Bernardo Glacier. They also indicate the accumulation zone does not extend as far east toward the crest of the SPI as previously mapped. Davies and Glasser (2012) indicate that over the last century the most rapid retreat was from 2000 to 2011.

In 1986 Bernardo the southern terminus of the glacier was nearly in contact with Tempano Glacier. The main terminus primarily ended on an outwash plain with a small proglacial lake developing. The northern terminus had retreated a short distance south from a peninsula. By 1998 the northern terminus had retreated into a wider, deeper lake basin, filled with icebergs. The main terminus is still mainly grounded on an outwash plain. A small lake has developed between Bernardo Glacier and Tempano Glacier to the south. By 2003 the northern terminus had retreated 2 km from 1986, the main terminus 1.5 km and the southern terminus 1.2 km. By 2015 the lake between Tempano and Bernardo Glacier had drained. The main terminus had retreated 1.5 km since 1986. In 2016 the northern terminus had retreated 3.5 km since 1986, the main terminus 2.5 km and the southern terminus 2.75 km. The largest change is the loss of the lake between Tempano and Bernardo Glacier which slow the retreat of the southern terminus. If this terminus retreat into the another lake basin that shared with the main and north terminus, this would likely destabilize the entire confluence region. The nearly 1 km retreat in a single year from 2015 to 2016 of the main terminus indicates the instability that will lead to further calving enhanced retreat. The retreat of this glacier fits the overall pattern of the SPI outlet glaciers, for example Chico Glacier and Lago Onelli Glaciers

1998 Landsat image. Red arrows indicate 1986 terminus location and yellow arrows the 2016 terminus location.

2003 Landsat image. Red arrows indicate 1986 terminus location and yellow arrows the 2016 terminus location. Main terminus beginning to retreat from outwash plain.

2015 Landsat image. Red arrows indicate 1986 terminus location and yellow arrows the 2016 terminus location. Note the considerable difference in main terminus versus one year later in 2016.