Changes in terrestrial organic matter input to the Mendeleev Ridge, western Arctic Ocean, during the Late Quaternary

Abstract

Hydrocarbons and glycerol dialkyl glycerol tetraethers (GDGTs) were analyzed in Late Pleistocene sediments of Core HLY0503-08JPC collected at the Mendeleev Ridge during the Healy-Oden Trans Arctic Expedition 2005 (HOTRAX'05) to investigate environmental changes in the western Arctic Ocean during the last full glacial cycle, ca. 130 kyr. Variations in long-chain n-alkane and GDGT concentrations correspond to alternated color banding, brown (interglacial/interstadial) and grayish (glacial/stadial) layers. Grayish layers are characterized by abundant higher plant n-alkanes and branched GDGTs, implying larger contribution of terrestrial plant and soil organic matter (OM) in glacial environments, possibly due to the deposition of fine-grained products of glacial erosion in the Amerasian basin. Lithic n-alkanes derived from mature OM show pronounced peaks, which can be classified into six types presumably indicative of various sediment sources. Some peaks are correlated to events of iceberg discharge and freshwater outbursts from proglacial lakes of the Eurasian and, possibly, Laurentide ice sheets, suggesting that other peaks may correspond to similar events.

Sedimentary organic matter and carbonate variations in the Chukchi Borderland in association with ice sheet and ocean-atmosphere dynamics over the last 155 kyr

“…TOC values at site PC1 are generally low, but nonetheless characterized by distinct peaks, in particular during MIS 6, 4 and 2. These results are consistent with a study from the nearby Mendeleev Ridge, where increased input of terrestrial organic matter was observed during cold periods associated with more efficient transport of organic matter from the land to the ocean (Yamamoto and Polyak, 2009). Yamamoto and Polyak (2009) also suggested that transport of terrestrial organic matter during cold episodes was associated with fine and muddy sediments at the Mendeleev Ridge as also observed in our record, where increases in TOC are mostly associated with low coarse fractions (Fig.…”

“…Because the carbonate-rich Canadian Arctic should be viewed as the primary source of detrital carbonate, while carbonate is rare or absent on the Siberian margins and in the eastern Arctic Ocean (Bischof et al, 1996), we suggest that our more carbonate-rich and coarser samples would have mostly derived from the Canadian margins. In contrast, samples with low coarse fraction and lower carbonate could be explained by advection of organic carbon from carbonatepoor areas such as the Siberian margins, consistent with the results of Yamamoto and Polyak (2009), and/or by weakening of carbonate transport to the Northwind Ridge. With regard to surface ocean current dynamics, Phillips and Grantz (2001) suggested that the relatively high detrital carbonate observed today at the Northwind Ridge would have been transported from the carbonate-rich Canadian Arctic via the Beaufort Gyre.…”

“…Because dilution of TOC by CaCO 3 may also explain part of the anti-correlation of the two variables, changes in detrital carbonate supply in response to a changing Beaufort Gyre may have caused the observed temporal variations without invoking changes in TOC. However, as mentioned in chapter 5.3, increases in organic matter input may be well expected in the area during cold periods (Yamamoto and Polyak, 2009) and therefore probably contributed to TOC increases.…”

Variability in transport of terrigenous material on the shelves and the deep Arctic Ocean during the Holocene

“…Understanding these dynamic processes is important for assessing modern and future changes in the Arctic. Parameters of past terrestrial input (e.g., past riverine discharge, coastal erosion) can serve as boundary conditions in models for a changing Arctic.While regional data on the Arctic Ocean sedimentary patterns exist (e.g., Stein & Fahl 2000;Stein, Schubert et al 2004;Yamamoto & Polyak 2009;Faux et al 2011), there is no comprehensive pan-Arctic summary of the present state of knowledge about Holocene sediment sources, transport mechanisms and deposition of terrigenous material in the Arctic Ocean. Variability through the Holocene (last 11 700 years) provides a basic reference frame for modern observations because it tracks a changing climate in the Arctic since the LGM and is punctuated by intervals of warmer and colder climates compared to those captured by modern observations (e.g., Łą cka et al 2015; this paper provides an overview focusing on the variability of sediment transport processes on the shallow shelf seas of the Arctic Ocean on different time scales (present-day observations and palaeo-records), as well as a summary focusing on the increasing extents of shelf seas since the beginning of the Holocene on a pan-Arctic scale with regard to the pathways of terrestrial input.…”

“…Today, shelf currents experience a strong seasonality with wind and ice as limiting factors (e.g., Harms & Karcher 1999;McClimans et al 2000;Sternberg et al 2001;Wegner et al 2005;Schulze & Pickart 2012). The surface distribution of riverine water and river-derived material shows strong interannual variability, mainly attributed to atmospheric vorticity variations over the adjacent Arctic Ocean in summer (Guay et al 2001;Macdonald et al 2002; ViscosiShirley et al 2003;Dmitrenko et al 2005; Bauch et al 2009;Yamamoto-Kawai et al 2009;Wegner et al 2013). On the shelves and slopes, at water depth below 100 m, currents do not show a seasonal cycle (e.g., Woodgate et al 2001).…”