The sensitivity of the Greenland Ice Sheet to climate change: Reconstructing the response of the Jakobshavn Isbræ during the Little Ice Age and Holocene thermal maximum

Synopsis: Humanity is now faced with the realities of a warming planet and a rapidly changing world. As society places increasing demands upon scientists to forecast future climate change and its impacts, there is new urgency in our collective efforts to understand and model the response of Earth’s systems to rapidly changing climate. We have funding from the National Science Foundation to reconstruct Greenland Ice Sheet fluctations (using glacier-fed lake sediment records and cosmogenic exposure dating of ice-sculpted bedrock) and summer temperatures (using chironomid assemblage and varve thickness temperature proxies from lake sediments). We are overlapping the youngest part of our reconstructions with remote sensing-based information collected over the historic interval as an aim to quantify the sensitivity of the western Greenland Ice Sheet to climate change. This is a preliminary study with the aim of generating pilot data and assessing the feasibility of a more comprehensive project.

Below: Same area as above Landsat image showing various ice limits of the Jakobshavn ice stream and surrounding land-based margins during the Holocene. Our study area spans from the Disko Bugt coastline to the present ice sheet margin. The black zone adjacent to the present (2000 AD) ice margin is the landsacpe covered by ice during the Little Ice Age.

We have two main objectives:

Objective 1: Determine the rate of retreat of the Jakobshavn margin during the early and middle Holocene, a time period that was warmer than today.
Using cosmogenic exposure dating of ice-eroded bedrock along a transect from the outer coast to the present ice sheet margin, we will determine the retreat rate of the ice sheet during this interval of warmer-than-present conditions.

Objective 2: Determine the timing of advance/retreat of the Jakobshavn ice margin during the Little Ice Age, quantify associated volumetric changes, and estimate the sensitivity of the margin to temperature change (Δvolume per °C).
By dating glacier meltwater-derived sediments deposited into lakes just beyond the LIA trimline, we can combine the timing of ice margin advance with its historically constrained pattern of retreat to determine the timing of ice margin change over a full advance/retreat cycle. Combining this with a local summer temperature reconstruction using chironomid paleothermometry, and ice volume changes from 3D mapping, we will quantify the ice margin’s sensitivity to climate change (e.g., Δvolume per °C).

*Please visit the webpages on lakes and rocks to learn more about our study sites. Also visit our gallery of photographs from the 2008 field season.