Sensitivity of the carbon cycle in the Arctic to climate change

Abstract

Abstract. The recent warming in the Arctic is affecting a broad spectrum of physical, ecological, and human/cultural systems that may be irreversible on century time scales and have the potential to cause rapid changes in the earth system. The response of the carbon cycle of the Arctic to changes in climate is a major issue of global concern, yet there has not been a comprehensive review of the status of the contemporary carbon cycle of the Arctic and its response to climate change. This review is designed to clarify key uncertainties and vulnerabilities in the response of the carbon cycle of the Arctic to ongoing climatic change. While it is clear that there are substantial stocks of carbon in the Arctic, there are also significant uncertainties associated with the magnitude of organic matter stocks contained in permafrost and the storage of methane hydrates beneath both subterranean and submerged permafrost of the Arctic. In the context of the global carbon cycle, this review demonstrates that the Arctic plays an important role in the global dynamics of both CO 2 and CH 4 . Studies suggest that the Arctic has been a sink for atmospheric CO 2 of between 0 and 0.8 Pg C/yr in recent decades, which is between 0% and 25% of the global net land/ocean flux during the 1990s. The Arctic is a substantial source of CH 4 to the atmosphere (between 32 and 112 Tg CH 4 /yr), primarily because of the large area of wetlands throughout the region. Analyses to date indicate that the sensitivity of the carbon cycle of the Arctic during the remainder of the 21st century is highly uncertain. To improve the capability to assess the sensitivity of the carbon cycle of the Arctic to projected climate change, we recommend that (1) integrated regional studies be conducted to link observations of carbon dynamics to the processes that are likely to influence those dynamics, and (2) the understanding gained from these integrated studies be incorporated into both uncoupled and fully coupled carbon-climate modeling efforts.

Modeling permafrost thaw and ecosystem carbon cycle under annual and seasonal warming at an Arctic tundra site in Alaska

“…Some evidence showed that terrestrial ecosystems (e.g., tundra) might be a weak C sink rather than a C source under global climate warming [Shaver et al, 2000;Smith et al, 2004;Zimov et al, 2006b;Hollingsworth et al, 2008;McGuire et al, 2009;Zhuang et al, 2010;Elmendorf et al, 2012;Lu et al, 2012], but other evidence points in the opposite direction [Belshe et al, 2013;Natali et al, 2014]. Our short-term and 50 year long projection showed that annual warming and winter warming increase the C sink strength rather than decrease C. Our study support that the tundra ecosystem will remain as a weak C sink at least in the first half of this century.…”

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

“…Previous studies have suggested that Arctic streams export a greater proportion of primary productivity as compared to temperate and tropical watersheds (Peterson et al 1986;Harvey et al 1997;Waddington and Roulet 1997;McGuire et al 2009). As temperatures warm in the Arctic and soils thaw, the balance of C fixed by plants and released, either to the atmosphere as CO 2 or CH 4 or in streams as DOC or dissolved inorganic C, is expected to change (McGuire et al 2002(McGuire et al , 2009), but the magnitude and direction of this change is unknown.…”

“…A significant proportion of primary production in Arctic ecosystems is exported as dissolved and particulate organic C in rivers (McGuire et al 2009), and mobilization of terrestrial nutrients during high-discharge events drives productivity in oligotrophic lakes and streams (Hobbie et al 1999;MacIntyre et al 2006). Constituent concentrations in Arctic streams vary with changing discharge due to snowmelt and/or rainfall as observed in many other places around the world.…”

Geothermal ecosystems as natural climate change experiments: The ForHot research site in Iceland as a case study

“…The typical cold conditions at high latitudes strongly constrain decomposition of organic material (McGuire et al 2009) and over time this has led to the build-up of organicmatter rich soils with relatively slow nutrient cycles in this region. As a consequence, northern high latitude soils store almost 30% of the global soil carbon (C) stocks (Scharlemann et al 2014), even if they only cover ca.…”