Desert dust and anthropogenic aerosol interactions in the Community Climate System Model coupled-carbon-climate model

Mahowald, N. M.; Lindsay, Keith; Rothenberg, Daniel; Doney, Scott C.; Moore, J. Keith; Thornton, P. E.; Randerson, James T.; Jones, Chris D.

doi:10.5194/bg-8-387-2011

Cited by 53 publications

(46 citation statements)

References 62 publications

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“…The dust model generates dust in regions with unvegetated, dry soils with strong winds and easily erodible soil . Interactions between the dust and ocean biogeochemistry modules has previously been investigated (Mahowald et al, 2011). Changes in dust deposition affect ocean productivity by perturbing iron limitation of nitrogen fixing organisms and ultimately impacts oceanic uptake of carbon dioxide in the model.…”

Section: Model Descriptionmentioning

confidence: 99%

“…Model runs were branched from a control run after 50 yr and subsequently integrated over a 130-yr period spanning 1870-2000, as described in more detail in Mahowald et al (2011). In addition to the "AEROSOL" simulation referred to in that paper, two additional ensemble members with volcanoes were set up and integrated for this study, branched from points set ten years apart.…”

Section: Ensemble Member Setupmentioning

confidence: 99%

“…The model used here is based on the NCAR Community Climate System Model Version 3 (CCSM3) as described in Collins et al (2006a) and Yeager et al (2006) and is run in a coupled configuration with atmosphere, land, ocean, and sea ice components with the addition of a fully-coupled carbon cycle with land and ocean components, as described in Thornton et al (2009) and Mahowald et al (2011). The model was configured identically to the one used in the aerosol experiments in Mahowald et al (2011), with the CAM atmosphere model component running at a T31 resolution (3.75 • × 3.75 • latitude by longitude grid) with 26 vertical levels (Collins et al, 2006b); it included estimates of historical volcanic forcing, as well as prognostic carbonaceous, sulfate, dust and sea salt aerosols and corresponding emissions varying over the time period 1870-2000 (Meehl et al, 2006).…”

Section: Model Descriptionmentioning

confidence: 99%

“…The model was configured identically to the one used in the aerosol experiments in Mahowald et al (2011), with the CAM atmosphere model component running at a T31 resolution (3.75 • × 3.75 • latitude by longitude grid) with 26 vertical levels (Collins et al, 2006b); it included estimates of historical volcanic forcing, as well as prognostic carbonaceous, sulfate, dust and sea salt aerosols and corresponding emissions varying over the time period 1870-2000 (Meehl et al, 2006). The time-varying volcanic forcing dataset (prescribing volcanic aerosol loading) used here, as well as in Meehl et al (2006), is derived from previous work by Ammann et al (2003).…”

Section: Model Descriptionmentioning

confidence: 99%

“…This study investigates the performance of one coupled carbon-climate model -the CCSM3 Mahowald et al, 2011) -by analyzing the responses by the ocean and land carbon cycle to volcanic eruptions during the period 1870-2000. This study differs from previous studies in several ways: It looks at multiple volcanoes over 130 yr, while focused on the volcanic forcing of climate and the impact on the carbon cycle using a different model and only for the Pinatubo eruption, and Brovkin et al (2010) looked at the role of eruptions over the last 1000 yr.…”

Section: Introductionmentioning

confidence: 99%

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Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

et al. 2012

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Abstract. Volcanic eruptions induce a dynamical response in the climate system characterized by short-term global reductions in both surface temperature and precipitation, as well as a response in biogeochemistry. The available observations of these responses to volcanic eruptions, such as to Pinatubo, provide a valuable method to compare against model simulations. Here, the Community Climate System Model Version 3 (CCSM3) reproduces the physical climate response to volcanic eruptions in a realistic way, as compared to direct observations from the 1991 eruption of Mount Pinatubo. The model's biogeochemical response to eruptions is smaller in magnitude than observed, but because of the lack of observations, it is not clear why or where the modeled carbon response is not strong enough. Comparison to other models suggests that this model response is much weaker over tropical land; however, the precipitation response in other models is not accurate, suggesting that other models could be getting the right response for the wrong reason. The underestimated carbon response in the model compared to observations could also be due to the ash and lava input of biogeochemically important species to the ocean, which are not included in the simulation. A statistically significant reduction in the simulated carbon dioxide growth rate is seen at the 90 % level in the average of 12 large eruptions over the period 1870-2000, and the net uptake of carbon is primarily concentrated in the tropics, with large spatial variability. In addition, a method for computing the volcanic response in model output without using a control ensemble is tested against a traditional methodology using two separate ensembles of runs; the method is found to produce similar results in the global average. These results suggest that not only is simulating volcanoes a good test of coupled carbon-climate models, but also that this test can be performed without a control simulation in cases where it is not practical to run separate ensembles with and without volcanic eruptions.

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Section: Model Descriptionmentioning

confidence: 99%

Section: Ensemble Member Setupmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

et al. 2012

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Large‐scale impact of Saharan dust on the North Atlantic Ocean circulation

Serra¹,

Avellaneda

Stammer³

2014

JGR Oceans

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The potential for a dynamical impact of Saharan mineral dust on the North Atlantic Ocean large-scale circulation is investigated. To this end, an ocean general circulation model forced by atmospheric fluxes is perturbed by an idealized, seasonally varying, net shortwave flux anomaly, as it results from remote sensing observations of aerosol optical thickness representing Saharan dust load in the atmosphere. The dust dynamical impact on the circulation is assessed through a comparison between perturbed and an unperturbed run. Results suggest that, following the dust-induced shortwave irradiance anomaly, a buoyancy anomaly is created in the Atlantic offshore the African coast, which over the course of the time propagates westward into the interior Atlantic while progressively subducting. Changes in the large-scale barotropic and overturning circulations are significant after 3 years, which coincides with the elapsed time required by the bulk of the buoyancy perturbation to reach the western boundary of the North Atlantic. Although small in amplitude, the changes in the meridional overturning are of the same order as interannual-to-decadal variability. Variations in the amplitude of the forcing lead to changes in the amplitude of the response, which is almost linear during the first 3 years. In addition, a fast, but dynamically insignificant, response can be observed to propagate poleward along the eastern boundary of the North Atlantic, which contributes to a nonlinear response in the subpolar region north of 40 N.

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The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions

Guieu

Aumont

Paytan

et al. 2014

Global Biogeochemical Cycles

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119

122

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In the vast Low Nutrient Low-Chlorophyll (LNLC) Ocean, the vertical nutrient supply from the subsurface to the sunlit surface waters is low, and atmospheric contribution of nutrients may be one order of magnitude greater over short timescales. The short turnover time of atmospheric Fe and N supply (<1 month for nitrate) further supports deposition being an important source of nutrients in LNLC regions. Yet, the extent to which atmospheric inputs are impacting biological activity and modifying the carbon balance in oligotrophic environments has not been constrained. Here, we quantify and compare the biogeochemical impacts of atmospheric deposition in LNLC regions using both a compilation of experimental data and model outputs. A metadata-analysis of recently conducted field and laboratory bioassay experiments reveals complex responses, and the overall impact is not a simple "fertilization effect of increasing phytoplankton biomass" as observed in HNLC regions. Although phytoplankton growth may be enhanced, increases in bacterial activity and respiration result in weakening of biological carbon sequestration. The application of models using climatological or time-averaged non-synoptic deposition rates produced responses that were generally much lower than observed in the bioassay experiments. We demonstrate that experimental data and model outputs show better agreement on short timescale (days to weeks) when strong synoptic pulse of aerosols deposition, similar in magnitude to those observed in the field and introduced in bioassay experiments, is superimposed over the mean atmospheric deposition fields. These results suggest that atmospheric impacts in LNLC regions have been underestimated by models, at least at daily to weekly timescales, as they typically overlook large synoptic variations in atmospheric deposition and associated nutrient and particle inputs. Inclusion of the large synoptic variability of atmospheric input, and improved representation and parameterization of key processes that respond to atmospheric deposition, is required to better constrain impacts in ocean biogeochemical models. This is critical for understanding and prediction of current and future functioning of LNLC regions and their contribution to the global carbon cycle.

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Desert dust and anthropogenic aerosol interactions in the Community Climate System Model coupled-carbon-climate model

Cited by 53 publications

References 62 publications

Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

Volcano impacts on climate and biogeochemistry in a coupled carbon–climate model

Large‐scale impact of Saharan dust on the North Atlantic Ocean circulation

The significance of the episodic nature of atmospheric deposition to Low Nutrient Low Chlorophyll regions

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