Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change

Abstract

Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets ( 14 C) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2 ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7 ka). In contrast, age-offsets were higher (3.0-5.0 ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0 ka) and Bølling-Allerød periods (14.5-12.9 ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were~10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events.

A multi-proxy reconstruction of environmental change spanning the last 37,000 years from Burial Lake, Arctic Alaska

“…This conclusion is consistent with the lack of evidence for YD alpine glacier advances in the central Brooks Range (Hamilton, 1982;Badding et al, 2013) and a review of paleoecological data showing similar to modern temperatures in northern Alaska (Kokorowski et al, 2008). However, this contrasts with regional evidence for the YD in northern Alaska that include low lake-levels and decreased effective moisture at Lake of the Pleistocene (Mann et al, 2002;Gaglioti et al, 2014) and floodplain incision on the Alaskan North Slope (Mann et al, 2010) from cooler and potentially drier conditions. Further, evidence for colder temperatures is inferred from fossil beetle assemblages along Noatak River (Elias, 2000) and from a negative d 18 O excursion from the Barrow ice wedge system on the Alaskan North Slope (Fig.…”

“…These intermediate sea levels would have reduced the extent of subaerial Bering Sea continental shelf exposure compared with the LGM lowstand. As a result, the transport distance of moisture-laden air masses from the North Pacific Ocean traveling towards Alaska would have been similar to that during the Lateglacial transition (14,000e16,000 cal yr BP) where notable increases in effective moisture and higher lake-levels are reported across interior and northern Alaska (Abbott et al, 2000;Mann et al, 2002;Finkenbinder et al, 2014;Gaglioti et al, 2014).…”

Impacts of shore expansion and catchment characteristics on lacustrine thermokarst records in permafrost lowlands, Alaska Arctic Coastal Plain

“…[60] and terrestrial deposits (e.g., Siberia: Wetterich et al [84]; Canada: Murton et al [68], Fritz et al [28]; Alaska: Kanevskiy et al [48], Wetterich et al [83]), thermokarst lake sediments are important paleo-archives for reconstructing environmental changes on millennial time scales. Numerous studies have focused on general paleo-limnological investigations of Late Quaternary lake sediments by using various sediment and biogeochemical proxies (Lenz et al [55]; diatoms: Biskaborn et al [8]; plant macrofossils: Gaglioti et al [31]). Some studies have concentrated on investigating thermokarst and geomorphological processes (Siberia: Biskaborn et al [9]; Morgenstern et al [66]; Schleusner et al [77]; Canada: Coulombe et al [19]; Fritz et al (under review) [27]; Alaska: Farquharson et al [24,25], reconstructing lake generations (e.g., [41,45,57]) and carbon cycling (carbon accumulation rates: Klein et al [51]; 14 C age offsets: Gaglioti et al [31]; carbon degradation: Lenz et al [57]; methane production potentials: Heslop et al [36]).…”

A bibliometric review on carbon cycling research during 1993–2013

“…The ranking of ''climate change '' increased from 4th in 1993-2002 to 3rd in 2003-2007, and to 2nd in 2008-2013. This increase reflects climate-change-relevant topics were given more and more scientific attention during the past two decades and a continued rising in popularity is expected in the future (Gaglioti et al 2014;Cornelissen and Makoto 2013). Similarly, ''soil respiration'', ''decomposition'', and ''respiration'' showed stable and continuous increases, suggesting that terrestrial systems regarding organic decomposition and soil respiration have become primary research focuses during the past two decades (Deng et al 2013;Cotton et al 2013).…”

“…Publication performance by institution (a) and by journal (b) from 1993 to 2013Environ Earth Sci were more research papers focusing on the impacts of arctic regions on global carbon cycling and/or their responses to climate change(Monier et al 2014;Tranvik 2014;Gaglioti et al 2014). ''Fire'' was an obscure keyword with 95th-ranking during 1998-2002, however, its ranking markedly increased to 54th and 34th during2003-2007 and 2008-2013, respectively.…”