et al. 2007). The sea ice-specific HBI called IP 25 (Ice Proxy with 25 carbon atoms)
is biosynthesised by sea ice diatoms (e.g., Belt et al. 2007) from the genus Haslea
(Belt et al. 2007; Belt and Müller 2013; Stoynova et al. 2013; Xiao et al. 2013) and
a species from the Pleurosigma genus (Pleurosigma stuxbergii var. rhomboides;
Brown et al. 2014).
HBIs (including IP 25 ) are preserved in sediment and laboratory based experiments showed their good resistance to transformations by photo-oxidation (in the
upper water layer), biodegradation (at the sediment-water interface; Belt et al. 2000;
Robson and Rowland 1986; Rontani et al. 2014), which makes it useful as a proxy
for sediments from the Holocene and as old as 2.2 Ma (Stein and Fahl 2012). IP 25 is
very sensitive and can be detected from <1 g of sediment, which enables detailed
and high resolution sediment core analyses with sub-decadal resolution (Belt et al.
2007).
The presence and variability of IP 25 in down-core sediments from several Arctic
regions, including the Barents Sea (Vare et al. 2010; Berben et al. 2014), Fram
Strait (Müller et al. 2009), northern Norway (Cabedo-Sanz et al. 2013), northern
Iceland (Massé et al. 2008; Andrews et al. 2009; Axford et al. 2011), the Canadian
Arctic Archipelago (Vare et al. 2009; Belt et al. 2007, 2008, 2010; Brown et al.
2011) and the eastern Arctic Ocean (Fahl and Stein 2012), has been interpreted as a
direct indication of palaeo spring sea ice coverage and its change over time.
The distribution of IP 25 in a sediment core correlates well with historic data of
sea ice occurrence (Massé et al. 2008; Alonso-Garcia et al. 2013), other sea ice
proxy data, such as IRD, bowhead whale remains (Vare et al. 2009) or dinoflagellates (Stein et al. 2014), and instrumental data (Müller et al. 2011), which supports
the applicability of this biomarker. Moreover, there is an established relationship
between IP 25 abundances from surface sediments in different Arctic locations and
known recent sea ice conditions derived from satellite data (Müller et al. 2011;
Navarro-Rodriguez et al. 2013; Stoynova et al. 2013; Xiao et al. 2013).
However, Belt et al. (2007) and Müller et al. (2011) point out that the absence of
IP 25 in marine (Arctic) sediments might reflect either a lack of sea ice or indicate a
permanent ice cover that prevents any algal growth. The additional use of the
phytoplankton-derived biomarker brassicasterol (or dinosterol) as an indicator of
open-water conditions facilitates the environmental reconstruction of ambiguous
IP 25 signals (Müller et al. 2009). Phytoplankton-IP 25 indices (“PIP 25 -Index”) might
be used for the semi-quantitative evaluation of palaeo sea ice conditions that can be
incorporated into models for forecasting further climate change. The PIP 25 index
accounts for the (spring/summer) algal activity beneath the sea ice (mainly ice
algae), at the ice-edge (ice and phytoplankton algae), and in ice-free areas (phytoplankton) and thus allows a rough estimate of the spatial and temporal extent of
the sea ice cover. The absence of both biomarkers might demonstrate a permanent
ice cover, whereas the absence of IP 25 with elevated levels of brassicasterol suggests ice-free conditions. On the other hand, the occurrence of high (but variable)
abundances of both biomarkers reflects the seasonal ice margin (Fig. 1; Belt and
Müller 2013).
New Methods in the Reconstruction of Arctic Marine …
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is biosynthesised by sea ice diatoms (e.g., Belt et al. 2007) from the genus Haslea
(Belt et al. 2007; Belt and Müller 2013; Stoynova et al. 2013; Xiao et al. 2013) and
a species from the Pleurosigma genus (Pleurosigma stuxbergii var. rhomboides;
Brown et al. 2014).
HBIs (including IP 25 ) are preserved in sediment and laboratory based experiments showed their good resistance to transformations by photo-oxidation (in the
upper water layer), biodegradation (at the sediment-water interface; Belt et al. 2000;
Robson and Rowland 1986; Rontani et al. 2014), which makes it useful as a proxy
for sediments from the Holocene and as old as 2.2 Ma (Stein and Fahl 2012). IP 25 is
very sensitive and can be detected from <1 g of sediment, which enables detailed
and high resolution sediment core analyses with sub-decadal resolution (Belt et al.
2007).
The presence and variability of IP 25 in down-core sediments from several Arctic
regions, including the Barents Sea (Vare et al. 2010; Berben et al. 2014), Fram
Strait (Müller et al. 2009), northern Norway (Cabedo-Sanz et al. 2013), northern
Iceland (Massé et al. 2008; Andrews et al. 2009; Axford et al. 2011), the Canadian
Arctic Archipelago (Vare et al. 2009; Belt et al. 2007, 2008, 2010; Brown et al.
2011) and the eastern Arctic Ocean (Fahl and Stein 2012), has been interpreted as a
direct indication of palaeo spring sea ice coverage and its change over time.
The distribution of IP 25 in a sediment core correlates well with historic data of
sea ice occurrence (Massé et al. 2008; Alonso-Garcia et al. 2013), other sea ice
proxy data, such as IRD, bowhead whale remains (Vare et al. 2009) or dinoflagellates (Stein et al. 2014), and instrumental data (Müller et al. 2011), which supports
the applicability of this biomarker. Moreover, there is an established relationship
between IP 25 abundances from surface sediments in different Arctic locations and
known recent sea ice conditions derived from satellite data (Müller et al. 2011;
Navarro-Rodriguez et al. 2013; Stoynova et al. 2013; Xiao et al. 2013).
However, Belt et al. (2007) and Müller et al. (2011) point out that the absence of
IP 25 in marine (Arctic) sediments might reflect either a lack of sea ice or indicate a
permanent ice cover that prevents any algal growth. The additional use of the
phytoplankton-derived biomarker brassicasterol (or dinosterol) as an indicator of
open-water conditions facilitates the environmental reconstruction of ambiguous
IP 25 signals (Müller et al. 2009). Phytoplankton-IP 25 indices (“PIP 25 -Index”) might
be used for the semi-quantitative evaluation of palaeo sea ice conditions that can be
incorporated into models for forecasting further climate change. The PIP 25 index
accounts for the (spring/summer) algal activity beneath the sea ice (mainly ice
algae), at the ice-edge (ice and phytoplankton algae), and in ice-free areas (phytoplankton) and thus allows a rough estimate of the spatial and temporal extent of
the sea ice cover. The absence of both biomarkers might demonstrate a permanent
ice cover, whereas the absence of IP 25 with elevated levels of brassicasterol suggests ice-free conditions. On the other hand, the occurrence of high (but variable)
abundances of both biomarkers reflects the seasonal ice margin (Fig. 1; Belt and
Müller 2013).
New Methods in the Reconstruction of Arctic Marine …
129