dc.contributor.author | Naafs, BDA | |
dc.contributor.author | Gallego-Sala, AV | |
dc.contributor.author | Inglis, GN | |
dc.contributor.author | Pancost, RD | |
dc.date.accessioned | 2017-01-18T16:21:31Z | |
dc.date.issued | 2017-02-10 | |
dc.description.abstract | Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are increasingly used to
reconstruct past terrestrial temperature and soil pH. Here we compare all available
modern soil brGDGT data (n=350) to a wide range of environmental parameters to
obtain new global temperature calibrations.
We show that soil moisture index (MI), a modeled parameter that also takes
potential evapotranspiration into account, is correlated to the 6-methyl brGDGT
distribution but does not significantly control the distribution of 5-methyl brGDGTs.
Instead, temperature remains the primary control on 5-methyl brGDGTs. We propose the following global calibrations: MAAT soil = 40.01 x MBT’5me − 15.25 (n=350, R2 22 = 23 0.60, RMSE = 5.3 °C) and growing degree days above freezing (GDD0 soil) = 14344.3 x MBT’5me - 4997.5 (n=350, R2 24 = 0.63, RMSE = 1779 °C).
Recent studies have suggested that factors other than temperature can impact
arid and/or alkaline soils dominated by 6-methyl brGDGTs. As such, we develop new
global temperature calibrations using samples dominated by 5-methyl brGDGTs only
(IR6me<0.5). These new calibrations have significantly improved correlation
coefficients and lower root mean square errors (RMSE) compared to the global
calibrations: MAATsoil’ = 39.09 x !"#!!"
! − 14.50 (n=177, R2 30 = 0.76, RMSE =
4.1 °C) and GDD0 soil’ = 13498.8 x !"#!!"
! − 4444.5 (n=177, R2 31 = 0.78, RMSE =
1326). We suggest that these new calibrations should be used to reconstruct terrestrial
climate in the geological past; however, care should be taken when employing these
calibrations outside the modern calibration rang | en_GB |
dc.description.sponsorship | This research was funded through the advanced ERC grant `The greenhouse earth
412 system' (T-GRES, project reference 340923). R.D.P. acknowledges the Royal Society
413 Wolfson Research Merit Award. | en_GB |
dc.identifier.citation | Available online 10 February 2017 | en_GB |
dc.identifier.doi | http://dx.doi.org/10.1016/j.orggeochem.2017.01.009 | |
dc.identifier.uri | http://hdl.handle.net/10871/25262 | |
dc.language.iso | en | en_GB |
dc.publisher | Elsevier | en_GB |
dc.rights.embargoreason | Publisher's policy. | en_GB |
dc.title | Refining the global branched glycerol dialkyl glycerol tetraether (brGDGT) soil temperature calibration | en_GB |
dc.type | Article | en_GB |
dc.identifier.issn | 0146-6380 | |
dc.description | This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record. | |
dc.identifier.journal | Organic Geochemistry | en_GB |