Concentration, sources and light absorption characteristics of dissolved organic carbon on a typical glacier, the northeastern Tibetan Plateau

Abstract

Abstract. Light-absorbing dissolved organic carbon (DOC) constitutes a major part of the organic carbon in the glacierized region. It has important influences on the carbon cycle and radiative forcing of glaciers. However, currently, few data are available in the glacierized region of the Tibetan Plateau (TP). In this study, DOC characteristics of a typical glacier (Laohugou glacier No. 12 (LHG glacier)) in the Northeastern TP were investigated. Generally, DOC concentrations on LHG glacier were comparable to other glacierized regions around the world. The average DOC concentrations in snowpits, surface snow, surface ice (superimposed ice) and proglacial streamwater were 332.4 ± 132.3 μg L−1, 229.3 ± 104.4 μg L−1, 425.8 ± 269.9 μg L−1, and 237.5 ± 95.6 μg L−1, respectively. It was estimated that the annual DOC flux released from this glacier was 6949.4 kg C yr−1, of which 43.2 % DOC was bioavailable and could be decomposed into CO2 within 28 days of its release. The mass absorption cross section (MAC) of DOC at 365 nm was 1.4 ± 0.4 m2 g−1 in snow and 1.3 ± 0.7 m2 g−1 in ice, similar to those of dust transported from adjacent deserts. Based on this finding and the significant relationship between DOC and Ca2+, it was proven that the main source of DOC of this glacier was mineral dust. The radiative forcing of DOC relative to black carbon (BC) was calculated to be 9.5 ± 8.4 % in snow and 0.1 ± 0.1 % in ice, respectively, implying the necessity of accounting for DOC in future radiative forcing investigations in the glacierized region on the TP, especially when these areas are covered by fresh snow.

Concentration, sources and light absorption characteristics of dissolved organic carbon on a medium-sized valley glacier, northern Tibetan Plateau

“…Ice sheets and mountain glaciers cover 11 % of the land surface of the Earth and store approximately 6 Pg (1 Pg = 10 15 g) of organic carbon, the majority of which (77 %) is in the form of dissolved organic carbon (DOC) (Hood et al, 2015). The annual global DOC release through glacial run-off is around 1.04 ± 0.18 Tg C (1 Tg = 10 12 g) (Hood et al, 2015).…”

“…Ice sheets and mountain glaciers cover 11 % of the land surface of the Earth and store approximately 6 Pg (1 Pg = 10 15 g) of organic carbon, the majority of which (77 %) is in the form of dissolved organic carbon (DOC) (Hood et al, 2015). The annual global DOC release through glacial run-off is around 1.04 ± 0.18 Tg C (1 Tg = 10 12 g) (Hood et al, 2015). Therefore, glaciers not only play an important role in the hydrological cycle by contributing to sea level (Jacob et al, 2012) and endorheic basins (Neckel et al, 2014), but also potentially influence the global carbon cycle (Anesio and Laybourn-Parry, 2012;Hood et al, 2015) in the context of accelerated glacial ice loss rates.…”

“…The annual global DOC release through glacial run-off is around 1.04 ± 0.18 Tg C (1 Tg = 10 12 g) (Hood et al, 2015). Therefore, glaciers not only play an important role in the hydrological cycle by contributing to sea level (Jacob et al, 2012) and endorheic basins (Neckel et al, 2014), but also potentially influence the global carbon cycle (Anesio and Laybourn-Parry, 2012;Hood et al, 2015) in the context of accelerated glacial ice loss rates. In addition, a large portion of glacier-derived DOC has proven to be highly bioavailable, influencing the balance of downstream ecosys-F. Yan et al: Concentration, sources and light absorption characteristics of dissolved organic carbon tems (Hood et al, 2009;Singer et al, 2012;Spencer et al, 2014).…”

“…Although DOC storage in ice sheets is much larger than that of mountain glaciers, the annual mountain glacierderived DOC dominates the global DOC release (Hood et al, 2015). Currently, there are studies on DOC concentrations, ages and compositions of glaciers in Alaska (Stubbins et al, 2012;Hood et al, 2009), DOC bioavailability of glaciers on the Tibetan Plateau (TP) and the Greenland Ice Sheet (Spencer et al, 2014;Lawson et al, 2014) and DOC storage and export of the whole glacier regions around the world (Hood et al, 2015).…”

“…Although DOC storage in ice sheets is much larger than that of mountain glaciers, the annual mountain glacierderived DOC dominates the global DOC release (Hood et al, 2015). Currently, there are studies on DOC concentrations, ages and compositions of glaciers in Alaska (Stubbins et al, 2012;Hood et al, 2009), DOC bioavailability of glaciers on the Tibetan Plateau (TP) and the Greenland Ice Sheet (Spencer et al, 2014;Lawson et al, 2014) and DOC storage and export of the whole glacier regions around the world (Hood et al, 2015). The sources of glacier DOC are diverse and include autochthonous or in situ biological activities (Anesio et al, 2009), allochthonous carbon derived from overridden soils and vegetation (Bhatia et al, 2010), terrestrial inputs (DOC deposition from vascular plants and dust) (Singer et al, 2012) and anthropogenic sources (Stubbins et al, 2012).…”