Radiolarian‐based transfer functions for estimating mean surface ocean temperatures and seasonal range

Abstract

Abstract. New radiolarian-based transfer functions to estimate sea surface temperature (SST) and seasonal range are presented. The transfer functions are based on the approach originated by Imbrie and Kipp [ 1971 ]. The transfer functions differ from previous studies in the following three important ways: (1) extensions to Q-mode factor analysis provide an objective method to cull species in the very diverse radiolarian population; (2) a log transform of the relative abundance data is used to normalize the species percent data; and, (3) rather than writing equations for specific seasons, which are not independent data sets, statistically independent equations are developed to predict mean annual sea surface temperatures as well as seasonal temperature range. One hundred and seventy surface sediment samples from the Pacific Ocean are used to generate the SST and season temperature range transfer functions. All samples were counted using a standardized radiolarian taxonomy. Forty one radiolarian species were used in the final regression equation. Q-mode factor analysis of this data set identified seven assemblages. These assemblages,

Mismatch between the depth habitat of planktonic foraminifera and the calibration depth of SST transfer functions may bias reconstructions

“…Assemblage or geochemistry data from taxa that are constrained to live in the photic zone because they, or their symbionts, are photosynthetic -for example diatoms (Koç Karpuz and Schrader, 1990) -can be used to calculate surface temperatures, but may generate biased results if the seasonality of the proxy production changes. Other micropalaeontological proxies that are not constrained to live in the photic zone, for example radiolarians (Pisias et al, 1997), risk the same biases as planktonic foraminifera transfer functions if the ocean thermal structure changes.…”

Seasonality in long-term climate change

“…Imbrie & Kipp (1971) described the calibration technique for marine proxies based on assemblages in marine core tops. It was applied to foraminifers (Mix et al, 1986), and radiolarian assemblages (Pisias et al, 1997) for the reconstruction of sea surface temperature annual means and seasonal ranges, but despite promising results, reconstructions of past seasonal ranges were not broadly pursued.…”

The last five glacial‐interglacial transitions: A high‐resolution 450,000‐year record from the subantarctic Atlantic

“…[4] Transfer functions applied to microfossil assemblages have been successfully used to reconstruct past sea surface temperatures (SST) [CLIMAP Project Members, 1981;Pisias et al, 1997;Zielinski et al, 1998;Abelmann et al, 1999;Cortese and Abelmann, 2002;Niebler et al, 2003]. Radiolarians are particularly promising in this respect for the study area, as they are highly diversified and well preserved in Southern Ocean sediments Cortese and Abelmann, 2002].…”