The Arctic sea ice biomarker IP25: a review of current understanding, recommendations for future research and applications in palaeo sea ice reconstructions

Abstract

a b s t r a c tIn recent years, a novel proxy for the past occurrence of Arctic sea ice has been proposed that is based on the variable marine sedimentary abundance of an organic geochemical lipid derived from sea ice diatoms in the spring. This lipid, termed IP 25 (Ice Proxy with 25 carbon atoms), is a highly branched isoprenoid mono-unsaturated alkene that appears to be sufficiently stable in sediments to permit meaningful palaeo sea ice reconstructions to be carried out over short-to long-term timescales. Since the first proposed use of IP 25 as a proxy for palaeo sea ice by Belt et al. (2007), a number of laboratories have measured this biomarker in Arctic sediments and it is anticipated that research activity in this area will increase further in the future. The content of this review is divided into a number of sections. Firstly, we describe the scientific basis for the IP 25 proxy and its initial discovery in Arctic sea ice, sedimenting particles and sediments. Secondly, we summarise the relatively few studies that have, to date, concentrated on examining the factors that influence the production and fate of IP 25 and we identify some areas of future research that need to be addressed in order to improve our understanding of IP 25 data obtained from sedimentary analyses. What is clear at this stage, however, it that the presence of IP 25 in Arctic marine sediments appears to represent a proxy measure of past seasonal sea ice rather than permanent or multi-year ice conditions. Thirdly, we highlight the importance of rigorous analytical identification and quantification of IP 25 , especially if measurements of this biomarker are going to be used for quantitative sea ice reconstructions, rather than qualitative analyses alone (presence/absence). Fourthly, we review some recent attempts to make the interpretations of IP 25 biomarker data more detailed and quantitative by combining sedimentary abundances with those of phytoplankton-and other sea ice-derived biomarkers. Thus, the bases for the so-called PIP 25 and DIP 25 indices are described, together with an overview of potential limitations, concluding that investigations into the use of these indices needs further research before their full potential can be realised. In the final section, we provide a summary of IP 25 -based palaeo sea ice reconstruction case studies performed to date. These case studies cover different Arctic regions and timescales spanning decades to tens of thousands of years.

Source identification of the Arctic sea ice proxy IP25

“…7) (a C 25 highly branched isoprenoid (HBI) lipid 8 ) has attracted considerable interest, not least because it possesses the unique attribute of being produced within the sea ice itself. Consistent with this sea ice origin, the occurrence of IP 25 in marine sediments shows a strong correlation, spatially, to seasonally ice-covered Arctic waters 9 , and, from a temporal perspective, IP 25 appears to be stable in sediments for millions of years 10 . Combined, these attributes of IP 25 have provided the foundation for decadal to millennial-scale sea ice reconstructions across the Arctic [9][10][11][12][13][14][15] .…”

Sea ice in the paleoclimate system: the challenge of reconstructing sea ice from proxies – an introduction

“…Belt et al, 2007). The manuscripts include a review of current understanding of the Arctic sea ice biomarker IP25 and of the related sea ice index called PIP 25 (Belt and Müller, 2013), regional analyses of surface sediment data from the Barents Sea (Navarro-Rodriguez et al, 2013), the Laptev and Kara seas (Xiao et al, 2013), the Labrador Sea and other circum-Arctic areas (Stoynova et al, 2013), in addition to examples of application to document sea ice changes during the Younger Dryas (Cabedo-Sanz et al, 2013). Although IP25 cannot be used in the circum-Antarctic Ocean as diatom taxa occurrence differs in the Northern and Southern Hemispheres and IP25 does not seem to be produced in the Southern Ocean, there are other biomarkers that may serve as proxies for Antarctic sea ice cover as rst proposed by Massé et al (2011).…”

Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

“…The ongoing severe reduction of Arctic sea ice is largely ascribed to anthropogenic effects, but the current rate of sea-ice reduction is much faster than predicted by models, with rates exceeding the expected effect from temperature change (IPCC, 2013). The factors controlling sea-ice variability are poorly understood, and the provision of sea-ice reconstructions extending back in time beyond the instrumental and satellite era is therefore critical (Masse et al, 2008;Müller et al, 2009;Stein et al, 2012;Belt and Müller, 2013;Collins et al, 2013;de Vernal et al, 2013;Weckstr€ om et al, 2013).…”