Details

Autor(en) / Beteiligte

• Foster, Louise C.
• Pearson, Emma J.
• Juggins, Steve
• Hodgson, Dominic A.
• Saunders, Krystyna M.
• Verleyen, Elie
• Roberts, Stephen J.

Titel

Development of a regional glycerol dialkyl glycerol tetraether (GDGT)–temperature calibration for Antarctic and sub-Antarctic lakes

Ist Teil von

• Earth and planetary science letters, 2016-01, Vol.433, p.370-379

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2016

Link zum Volltext

Quelle

ScienceDirect

Beschreibungen/Notizen

• A regional network of quantitative reconstructions of past climate variability is required to test climate models. In recent studies, temperature calibration models based on the relative abundances of sedimentary glycerol dialkyl glycerol tetraethers (GDGTs) have enabled past temperature reconstructions in both marine and terrestrial environments. Nevertheless, to date these methods have not been widely applied in high latitude environments due to poor performance of the GDGT–temperature calibrations at lower temperatures. To address this we studied 32 lakes from Antarctica, the sub-Antarctic Islands and Southern Chile to: 1) quantify their GDGT composition and investigate the environmental controls on GDGT composition; and 2) develop a GDGT–temperature calibration model for inferring past temperatures from Antarctic and sub-Antarctic lakes. GDGTs were found in all 32 lakes studied and in 31 lakes branched GDGTs (brGDGTs) were the dominant compounds. Statistical analyses of brGDGT composition in relation to temperature, pH, conductivity and water depth showed that the composition of brGDGTs is strongly correlated with mean summer air temperature (MSAT). This enabled the development of the first regional brGDGT–temperature calibration for use in Antarctic and sub-Antarctic lakes using four brGDGT compounds (GDGT-Ib, GDGT-II, GDGT-III and GDGT-IIIb). A key discovery was that GDGT-IIIb is of particular importance in cold lacustrine environments. The addition of this compound significantly improved the model's performance from r2=0.67, RMSEP-LOO (leave-one-out)=2.23 °C, RMSEP-H (h-block)=2.37 °C when applying the re-calibrated global GDGT–temperature calibration to our Antarctic dataset to r2=0.83, RMSEP-LOO=1.68 °C, RMSEP-H=1.65 °C for our new Antarctic calibration. This shows that Antarctic and sub-Antarctic, and possibly other high latitude, palaeotemperature reconstructions should be based on a regional GDGT–temperature calibration where specific compounds can be identified and included to improve model performance. Finally, downcore temperature reconstructions using the new Antarctic brGDGT–temperature calibration were tested in sub-Antarctic Fan Lake from South Georgia providing a proof of concept for the new calibration model in the Southern Hemisphere. •GDGTs present in all Antarctic and sub-Antarctic lakes studied.•Temperature is the primary environmental control on branched GDGT composition.•We developed the first Antarctic and sub-Antarctic lake GDGT–temperature calibration.•Relationship between GDGT-IIIb and temperature is of particular importance.•Downcore application showed good correlation with other palaeoenvironmental records.