Browsing by Author "Cosentino, N. J."

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    Does Satellite Chlorophyll-a Respond to Southernmost Patagonian Dust? A Multi-year, Event-Based Approach
    (2020) Cosentino, N. J.; Ruiz-Etcheverry, L. A.; Bia, G. L.; Simonella, L. E.; Coppo, R.; Torre, G.; Saraceno, M.; Tur, V. M.; Gaiero, D. M.
    Mineral aerosols may affect global climate indirectly by enhancing net primary productivity (NPP) upon deposition to the oceans and associated atmosphere-to-ocean CO2 flux. This mechanism is hypothesized to have contributed significantly to the last interglacial-to-glacial climatic transition. However, the dust-NPP connection remains contentious for the present-day climate system. We analyze the impact of southernmost Patagonian dust emissions on southwestern Atlantic Ocean continental shelf and proximal open ocean satellite chlorophyll-a concentration. We use the first decadal time series of surface dust mass flux in southern Patagonia, along with in situ visibility data, to model dust emission, transport, and deposition to the ocean. We then perform a dust event-based analysis of chlorophyll-a time series, using a novel approach by which time series are corrected for post-depositional particle advection due to ocean currents. Finally, we performed chemical analysis of iron in dust samples, a key micronutrient limiting phytoplankton biomass in high-nutrient, low-chlorophyll oceans such as offshore of the 200-m isobath off Patagonia. We find no compelling evidence for an influence of dust as an enhancer of phytoplankton biomass either on shelf or proximal open ocean waters of the southwestern Atlantic Ocean. For open ocean waters this is consistent with a lack of source-inherited bioavailable iron in dust samples. Future case studies addressing similar questions should concentrate on dust sources with identified high contents of bioavailable iron, particularly in the Southern Hemisphere where atmospheric processing of iron is weak.
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    Global-Krigger: A Global Kriging Interpolation Toolbox With Paleoclimatology Examples
    (2023) Cosentino, N. J.; Opazo, N. E.; Lambert, F.; Osses, A.; van 't Wout, E.
    Many applications in Earth sciences require spatial prediction, that is, obtaining a continuous scalar field from a set of discrete scalar data points on the Earth's surface. Such applications include model data comparisons and derivation of continuous scalar fields as input for Earth system models. The advantage of kriging as an interpolation method is that it provides predictions with confidence intervals for data sets of irregularly distributed points in space. However, the theory of kriging for non-Euclidean domains such as oblate spheroids (e.g., the Earth's surface) is poorly developed, and existing kriging algorithms for global interpolation oftentimes cannot guarantee the validity of their predictions. Here, we present Global-Krigger, a new kriging interpolation algorithm adapted for local to global applications that (a) incorporates a numerical check to guarantee that the necessary conditions for the kriging system of linear equations are met, and (b) derives a combined uncertainty field due both to spatial variations in data density and measurement error. The robustness of the method is demonstrated by cross-validating predictions against reanalysis fields of traditional climatological scalar variables. We also show an example application in paleoclimatology for Holocene mineral dust deposition fluxes. The toolbox includes a user-friendly graphical user interface that guides users through a range of choices during data pre-interpolation analysis, kriging, and post-processing.Plain Language Summary Many climatic variables such as temperature and precipitation are measured by monitoring stations on the Earth's surface at irregularly distributed locations. Similarly, paleoclimatic proxy variables are available at specific locations where paleoclimatic archives such as marine sediment cores have been retrieved. Such data sets can be used to guide Earth system simulations, but this works best when they are available as a regular grid. Kriging is an interpolation method that produces regular grids from irregularly distributed measurements. However, while kriging theory is well-developed for measurements on a plane surface, its application on curved surfaces is problematic. To improve this, we have developed Global-Krigger, a user-friendly kriging interpolation toolbox for the surface of the Earth. It incorporates new tests to check the validity of kriging results on curved surfaces. The toolbox also provides a quantification of the interpolation uncertainty, taking into account both the uncertainty of the measurements and the spatial distribution of the measurement sites. We show that our algorithm gives robust results by applying it to a sub-sample of known modern climatology fields, and also provides a paleoclimatic application for Holocene mineral dust deposition fluxes. Finally, we develop a graphical user interface to guide users in the process of kriging.
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    Is Dust Derived From Shrinking Saline Lakes a Risk to Soil Sodification in Southern South America?
    (2022) Borda, L. G.; Cosentino, N. J.; Iturri, L. A.; Garcia, M. G.; Gaiero, D. M.
    Dry lakebeds exposed by shrinking water bodies in arid regions constitute sodium (Na)-rich mineral dust emission hotspots that may potentially affect agriculture through soil sodification. However, no soluble Na mass balance has so far been attempted. We modeled 13 years (2005-2017) of dust emission from Mar Chiquita (MC), the most extensive shrinking saline lake in South America. Based on a chemical characterization of dust, we found that a mean similar to 15-150 mg m(-2) of soluble Na was deposited 300 km from the source during the season of strongest dust emissions. We estimated the impact of this atmospheric input on 13 agricultural soils, with different rainfall regimes and water holding capacities. At most sites, dust-equilibrated infiltrated rainfall water had a Na concentration 8-7,000 times lower than the lowest concentration threshold proposed to trigger sodification. Additionally, this rainfall water is diluted similar to 2-20 times as it infiltrates in saturated soils, and its sodium adsorption ratio is probably reduced due to the abundance of soluble calcium and magnesium in the soil solution. Thus, there is no risk of short-term, seasonal sodification, except possibly at two sites and in close proximity to the dust source (<50 km), where dust deposition is maximum. At these sites, we estimated potential dust-related rises in the proportion of soil exchangeable Na. Under scenarios of enhanced salt-rich dust emissions from shrinking lakes in the twenty-first century, agricultural soils close to salt-rich dust sources worldwide should be monitored for potential Na enrichment related to Na-rich dust.
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    Present-Day Patagonian Dust Emissions: Combining Surface Visibility, Mass Flux, and Reanalysis Data
    (AMER GEOPHYSICAL UNION, 2021) Cosentino, N. J.; Gaiero, D. M.; Lambert, F.
    The magnitude of the climatic forcing associated with mineral dust aerosols remains uncertain due in part to a lack of observations on dust sources. While modeling and satellite studies provide spatially extensive constraints, they must be supported by surface-validating dust monitoring. Southern South America is the main dust source to the southern oceans (>45 degrees S), a region of low biological productivity potentially susceptible to increased micronutrient fertilization through dust deposition, as well as one of the main dust sources to Antarctica, implying long-range transport of dust from Patagonia and potentially affecting snow cover albedo. We present multiyear time series of dust-related visibility reduction (DRVR) and dust mass flux in Patagonia. We find that local DRVR is partly controlled by long-term (i.e., months) water deficit, while same-day conditions play a smaller role, reflective of water retention properties of fine-grained dust-emitting soils in low-moisture conditions. This is supported independently by reanalysis data showing that large-scale dust outbreaks are usually associated with anomalously high long-term water deficit. By combining visibility data, surface dust sampling, and particle dispersion modeling, we derive regional dust emission rates. Our results suggest that the inclusion of long-term soil hydrologic balance parameterizations under low-moisture conditions may improve the performance of dust emission schemes in Earth system models.