Warm times/Cold times

Warm times/Cold times: Reconstructing Iceland's climate and environment since the last glaciation to evaluate the impact of future climate change.

In the Warm times/Cold times project we have combined the research efforts of specialists from three different research fields: marine geology, terrestrial paleoenvironments, and glacier modeling, to reconstruct the paleoclimate history of Iceland from the Last Glacial Maximum to present day. We have utilized continuous marine sediment archives to address two primary questions:

  • What was the timing and magnitude of the Last Glacial Maximum in Iceland, and the pattern of ice recession during deglaciation?
  • When was Iceland deglaciated, and what were the terrestrial and near-shore environmental characteristics at this time?

We base our study on continuous proxy records of environmental change at high resolution (sub-decadal to century sampling intervals) for the entire period since the Last Glacial Maximum for the marine realm, and for the entire Holocene from key lakes. In 2003 we brought the DOSECC’s GLAD200 core rig to Iceland to core three large lakes; Hestvatn in South Iceland, Hvítárvatn in Central Iceland and Haukadalsvatn in NW Iceland. These records allow us to address three larger questions of recognized importance:

  • Did some of the extant large ice caps disappear in the early Holocene, and if so, what is the timing of glacier regrowth and subsequent glacier fluctuations in the late Holocene?
  • What is the magnitude and timing of summer temperature (ocean and land) and terrestrial vegetation change through the Holocene?
  • Is there a natural cyclicity in Holocene environmental change on Iceland as has been reported from the adjacent oceans and from the Greenland Ice Sheet?

Icelandic marine and lake sediments are particularly well suited to answer these questions because of strategically situated basins containing continuous time-series of key proxies. Efficient glacial erosion and soft bedrock result in high lacustrine sedimentation rates (up to 5 m ka-1). Accurate dating in both marine and terrestrial realms is possible with the development of AMS 14C dating and the presence of diagnostic tephras of known age. Furthermore, Iceland’s sensitivity to changes in North Atlantic circulation is expected to produce a high signal-to-noise ratio, resulting in unambiguous signals. Modeling of Iceland’s ice caps in the past will be based on climate proxies derived from the lake and marine records. Once the model is calibrated with the paleo-data, it can be used to predict ice-cap status under a range of future climate scenarios.