Susan M. Natali

Bio: Susan M. Natali is an academic researcher from Woods Hole Research Center. The author has contributed to research in topics: Permafrost & Tundra. The author has an hindex of 30, co-authored 81 publications receiving 5336 citations. Previous affiliations of Susan M. Natali include Woods Hole Oceanographic Institution & University of Florida.

Climate change and the permafrost carbon feedback

Abstract: Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to target poorly understood aspects of permafrost carbon dynamics.

Increased plant productivity in Alaskan tundra as a result of experimental warming of soil and permafrost

Abstract: Summary 1. The response of northern tundra plant communities to warming temperatures is of critical concern because permafrost ecosystems play a key role in global carbon (C) storage, and climate-induced ecological shifts in the plant community will affect the transfer of carbon-dioxide between biological and atmospheric pools. 2. This study, which focuses on the response of tundra plant growth and phenology to experimental warming, was conducted at the Carbon in Permafrost Experimental Heating Research project, located in the northern foothills of the Alaska Range. We used snow fences coupled with spring snow removal to increase deep-soil temperatures and thaw depth (winter warming), and open-top chambers to increase summer air temperatures (summer warming). 3. Winter warming increased wintertime soil temperature (5–40 cm) by 2.3 °C, resulting in a 10% increase in growing season thaw depth. Summer warming significantly increased growing season air temperature; peak temperature differences occurred near midday when summer warming plots were approximately 1.0 °C warmer than ambient plots. 4. Changes in the soil environment as a result of winter warming treatment resulted in a 20% increase in above-ground biomass and net primary productivity (ANPP), while there was no detected summer warming effect on ecosystem-level ANPP or biomass. Both summer and winter warming extended the growing season through earlier bud break and delayed senescence, despite equivalent snow-free days across treatments. As with ANPP, winter warming increased canopy N mass by 20%, while there was no summer warming effect on canopy N. 5. The warming-mediated increase in N availability, coupled with phenological shifts, may have driven higher rates of ANPP in the winter warming plots, and the lack of ecosystem-level N and ANPP response to summer warming suggest continued N limitation in the summer warming plots. 6. Synthesis: These results highlight the role of soil and permafrost dynamics in regulating plant response to climate change and provide evidence that warming may promote greater C accumulation in tundra plant biomass. While warming temperatures are expected to enhance microbial decomposition of the large pool of organic matter stored in tundra soils and permafrost, these respiratory losses may be offset, at least in part, by warming-mediated increases in plant growth.

Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils

Abstract: A meta-analysis of soil incubation studies from the permafrost zone suggests that thawing under aerobic conditions, which releases CO2, will strengthen the permafrost carbon feedback more than waterlogged systems, which releases CO2 and CH4. Increasing temperatures in northern high latitudes are causing permafrost to thaw1, making large amounts of previously frozen organic matter vulnerable to microbial decomposition2. Permafrost thaw also creates a fragmented landscape of drier and wetter soil conditions3,4 that determine the amount and form (carbon dioxide (CO2), or methane (CH4)) of carbon (C) released to the atmosphere. The rate and form of C release control the magnitude of the permafrost C feedback, so their relative contribution with a warming climate remains unclear5,6. We quantified the effect of increasing temperature and changes from aerobic to anaerobic soil conditions using 25 soil incubation studies from the permafrost zone. Here we show, using two separate meta-analyses, that a 10 °C increase in incubation temperature increased C release by a factor of 2.0 (95% confidence interval (CI), 1.8 to 2.2). Under aerobic incubation conditions, soils released 3.4 (95% CI, 2.2 to 5.2) times more C than under anaerobic conditions. Even when accounting for the higher heat trapping capacity of CH4, soils released 2.3 (95% CI, 1.5 to 3.4) times more C under aerobic conditions. These results imply that permafrost ecosystems thawing under aerobic conditions and releasing CO2 will strengthen the permafrost C feedback more than waterlogged systems releasing CO2 and CH4 for a given amount of C.

Expert assessment of vulnerability of permafrost carbon to climate change

Abstract: Approximately 1700 Pg of soil carbon (C) are stored in the northern circumpolar permafrost zone, more than twice as much C than in the atmosphere. The overall amount, rate, and form of C released to the atmosphere in a warmer world will influence the strength of the permafrost C feedback to climate change. We used a survey to quantify variability in the perception of the vulnerability of permafrost C to climate change. Experts were asked to provide quantitative estimates of permafrost change in response to four scenarios of warming. For the highest warming scenario (RCP 8.5), experts hypothesized that C release from permafrost zone soils could be 19–45 Pg C by 2040, 162–288 Pg C by 2100, and 381–616 Pg C by 2300 in CO2 equivalent using 100-year CH4 global warming potential (GWP). These values become 50 % larger using 20-year CH4 GWP, with a third to a half of expected climate forcing coming from CH4 even though CH4 was only 2.3 % of the expected C release. Experts projected that two-thirds of this release could be avoided under the lowest warming scenario (RCP 2.6). These results highlight the potential risk from permafrost thaw and serve to frame a hypothesis about the magnitude of this feedback to climate change. However, the level of emissions proposed here are unlikely to overshadow the impact of fossil fuel burning, which will continue to be the main source of C emissions and climate forcing.

Tundra soil carbon is vulnerable to rapid microbial decomposition under climate warming

Abstract: Release of carbon previously locked in permafrost is a potentially important positive climate feedback. Now metagenomics reveal the vulnerability of active-layer soil carbon to warming-induced microbial decomposition in Alaskan tundra.

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Climate Change 2007: The Physical Science Basis.

Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

Climate Change 2007: Impacts, Adaptation and Vulnerability.

Abstract: Impatti, adattamento e vulnerabilita Le cause e le responsabilita dei cambiamenti climatici sono state trattate sul numero di ottobre della rivista Cda. Approfondiamo l’argomento presentando il documento: “Cambiamenti climatici 2007: impatti, adattamento e vulnerabilita” votato ad aprile 2007 dal secondo gruppo di lavoro del Comitato Intergovernativo sui Cambiamenti Climatici (Intergovernmental Panel on Climate Change). Si tratta del secondo di tre documenti che compongono il quarto rapporto sui cambiamenti climatici.

Climate change and the permafrost carbon feedback

Abstract: Large quantities of organic carbon are stored in frozen soils (permafrost) within Arctic and sub-Arctic regions. A warming climate can induce environmental changes that accelerate the microbial breakdown of organic carbon and the release of the greenhouse gases carbon dioxide and methane. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emission from these regions and their impact on climate change remain uncertain. Here we find that current evidence suggests a gradual and prolonged release of greenhouse gas emissions in a warming climate and present a research strategy with which to target poorly understood aspects of permafrost carbon dynamics.