A Late Quaternary climate record based on long-chain diol proxies from the Chilean margin

Abstract

Abstract. In this study we have applied different indices based on long-chain diols, i.e., the long-chain diol index (LDI) as a proxy for past SST, the diol index as an indicator of past upwelling conditions, and the nutrient diol index (NDI) as a proxy for nitrate and phosphate concentrations in seawater. The proxies were analyzed in marine sediments recovered at ODP Site 1234, located within the Peru–Chile upwelling system, with a ∼2 kyr resolution covering the last 150 kyr. We also generated TEX86H and U37K′ temperature and planktonic δ18O records, as well as total organic carbon (TOC) and accumulation rates (ARs) of TOC and lipid biomarkers (i.e., C37 alkenones, GDGTs, dinosterol, and loliolide) to reconstruct past phytoplankton production. The LDI-derived SST record covaries with TEX86H- and U37K′-derived SST records as well as with the planktonic δ18O record, implying that the LDI reflects past SST variations at this site. TOC and phytoplankton AR records indicate increased export production during the last interglacial (MIS 5), simultaneous with a peak in the abundance of preserved Chaetoceros diatoms, suggesting intensified upwelling during this period. The diol index is relatively low during the upwelling period, but peaks before and after this period, suggesting that Proboscia diatoms were more abundant before and after the period of upwelling. The NDI reveals the same trends as the diol index, suggesting that the input of nitrate and phosphate was minimal during upwelling, which is unrealistic. We suggest that the diol index and NDI should perhaps be considered as indicators for Proboscia productivity instead of upwelling conditions or nutrient concentrations.

Southern Ocean temperature records and ice-sheet models demonstrate rapid Antarctic ice sheet retreat under low atmospheric CO2 during Marine Isotope Stage 31

“…Thus, we chose to use the long chain Diol Index (LDI) to reconstruct the SSTs at the Antarctic margin. This newly developed proxy for paleotemperatures (see Lopes dos Santos et al, 2013;de Bar et al, 2018), is based on the relative abundances of lipids with chain length of 28 and 30 carbon atoms containing two alcohol groups (long chain alkyl 1,13-and 1,15-diols; C 28 1,13-diol, C 30 1,13-diol and C 30 1,15-diol). In the marine environment, these long chain diols have been found in diatoms and marine algae .…”

A new age model for the Pliocene of the southern North Sea basin: a multi-proxy climate reconstruction

“…The mPWP is almost entirely covered by the oxygen isotope age-tuned interval of the Hank record, which starts after the hiatus that marks the M2 event. This mPWP interval is correlated with the Poederlee Formation and Oorderen Sands Member (of the Lillo Formation) located in Belgium (De Schepper et al, 2009a;Louwye and De Schepper, 2010). The average TEX 86 (10 • C) and U K 37 (16 • C) reconstructed SSTs over the mPWP interval show good agreement with the PRISM3 model reconstructions for February (10.4 • C) and August (16.7 • C; Dowsett et al, 2009).…”

“…The hiatus at Hank representing the M2 glacial event is also recognized in sequences from the Coralline Crag in the English North Sea (Williams et al, 2009), the Poederlee and Lillo formations in the Belgian North Sea (De Schepper et al, 2009a;Louwye and De Schepper, 2010) and possibly the Nordic Seas (Fig. 1, Risebrobakken et al, 2016).…”

A new age model for the Pliocene of the Southern North Sea Basin: evidence for asynchronous shifts of marine and terrestrial climate

“…In late Pliocene sediments from the central Mediterranean, LDI SST estimates were slightly lower than U K ʹ 37 SSTs, however this was within the error range of the proxies (Plancq et al, 2015). Due to the recent advent of the 585 LDI proxy, and the scarcity of other multi-proxy studies (De Bar et al, 2018;Lattaud et al, 2018) comparing the LDI to U K ʹ 37 and TEX 86 SSTs in the same sediment samples, further discussion on this topic is limited.…”