Shutting down dust emission during the middle Holocene drought in the Sonoran Desert, Arizona, USA

Geology ◽  
2021 ◽  
Author(s):  
Guy Tau ◽  
Onn Crouvi ◽  
Yehouda Enzel ◽  
Nadya Teutsch ◽  
Paul Ginoux ◽  
...  
Keyword(s):  
Sonoran Desert ◽  
Mojave Desert ◽  
Vegetation Change ◽  
Dust Emission ◽  
Major Elements ◽  
Sediment Supply ◽  
Transport Pathways ◽  
Middle Holocene ◽  
Dust Sources ◽  
Montezuma Well

Long-term relationships between climate and dust emission remain unclear, with two prevailing but opposite hypotheses for effects of climate shifts: (1) increased dust emission due to increasing aridity imposing a vegetation change, or (2) decreased dust emission due to increasing aridity which imposes less stormy climate and reduced sediment supply. Here we test these hypotheses by analyzing an ~11-m-long core archiving Holocene dust trapped in Montezuma Well, a natural sinkhole in Arizona (southwestern United States), alongside current dust sources and transport pathways. Major elements indicate that Montezuma Well sediments originate from two end members: local carbonate bedrock and external siliceous dust. Core sediments are similar to the adjacent siliceous soils accumulated atop the bedrock, pointing to their eolian origin. Particle-size distributions reveal fine dust transported during winter from the northwestern Sonoran Desert and the Mojave Desert and coarse dust transported during summer from the southwestern Sonoran Desert, similar to current climate systems and dust pathways. A survey of potential dust sources indicates that current summer and winter dust sources in the Sonoran Desert are under a supply-limited state. Dust fluxes were higher during wetter phases of the Holocene when winter sources dominated. During the middle Holocene drought, dust fluxes were minimal and dominated by summer sources until dust input ceased as drought conditions did not produce enough floods to refill sources with sediments. We propose that in the Sonoran Desert, dust emission is strongly connected with climate, increasing during humid intervals and enhanced by fluvial sediment replenishment at dust sources.

scholarly journals Supplemental Material: Shutting down dust emission during the middle Holocene drought in the Sonoran Desert, Arizona, USA

2021 ◽  
Author(s):  
Guy Tau ◽  
et al.
Keyword(s):  
Sonoran Desert ◽  
Dust Emission ◽  
Middle Holocene

Detailed description of the methods and the analyses results.<br>

scholarly journals Identification of Dust Sources in a Saharan Dust Hot-Spot and Their Implementation in a Dust-Emission Model

2018 ◽  
Vol 11 (1) ◽  
pp. 4 ◽  
Author(s):  
Stefanie Feuerstein ◽  
Kerstin Schepanski
Keyword(s):  
Mineral Dust ◽  
Dust Emission ◽  
Sediment Supply ◽  
Emission Model ◽  
Atmospheric Dust ◽  
Dust Source ◽  
Dust Sources ◽  
Dust Load ◽  
Supply Information ◽  
Sentinel 2

Although mineral dust plays a key role in the Earth’s climate system and in climate and weather prediction, models still have difficulties in predicting the amount and distribution of mineral dust in the atmosphere. One reason for this is the limited understanding of the distribution of dust sources and their behavior with respect to their spatiotemporal variability in activity. For a better estimation of the atmospheric dust load, this paper presents an approach to localize dust sources and thereby estimate the sediment supply for a study area centered on the Aïr Massif in Niger with a north–south extent of 16 ∘ –22 ∘ N and an east–west extent of 4 ∘ –12 ∘ E. This approach uses optical Sentinel-2 data at visible and near infrared wavelengths together with HydroSHEDS flow accumulation data to localize ephemeral riverbeds. Visible channels from Sentinel-2 data are used to detect sand sheets and dunes. The identified sediment supply map was compared to the dust source activation frequency derived from the analysis of Desert-Dust-RGB imagery from the Meteosat Second Generation series of satellites. This comparison reveals the strong connection between dust activity, prevailing meteorology and sediment supply. In a second step, the sediment supply information was implemented in a dust-emission model. The simulated emission flux shows how much the model results benefit from the updated sediment supply information in localizing the main dust sources and in retrieving the seasonality of dust activity from these sources. The described approach to characterize dust sources can be implemented in other regional model studies, or even globally, and can thereby help to get a more accurate picture of dust source distribution and a more realistic estimation of the atmospheric dust load.

Late Wisconsin Macrofossil Records of Desert Vegetation in the American Southwest

1983 ◽  
Vol 19 (2) ◽  
pp. 256-264 ◽  
Author(s):  
W. Geoffrey Spaulding
Keyword(s):  
Sonoran Desert ◽  
Mojave Desert ◽  
American Southwest ◽  
Early Holocene ◽  
Desert Vegetation ◽  
Middle Holocene ◽  
Vegetation Mosaic ◽  
Desert Scrub

AbstractUntil recently, the oldest-known packrat (Neotoma spp.) midden records of desert scrub vegetation were less than 10,500 yr old and were restricted to altitudes below 300 m in the northern Sonoran Desert. Recent discovery of macrofossil assemblages in the Mojave Desert extends the record of desert vegetation back to 14,800 yr ago and to altitudes as high as 910 m. Although xerophytic conifer woodland was widespread in current desert habitats during the Late Wisconsin and early Holocene, the development of extensive desert vegetation was not delayed until the beginning of the middle Holocene. A regional vegetation mosaic of desert scrub and woodland existed at altitudes below 1000 m in the Mojave Desert during the last part of the Late Wisconsin.

scholarly journals Late Quaternary geochronologic record of soil formation and erosion: Effects of climate change on Mojave Desert hillslopes (Nevada, USA)

Geology ◽  
2021 ◽  
Author(s):  
L.P. Persico ◽  
L.D. McFadden ◽  
J.R. McAuliffe ◽  
T.M. Rittenour ◽  
T.E. Stahlecker ◽  
...  
Keyword(s):  
Climate Change ◽  
Mojave Desert ◽  
Vegetation Change ◽  
Climatic Factors ◽  
Late Quaternary ◽  
Perennial Grass ◽  
Soil Development ◽  
Grass Cover ◽  
The Holocene ◽  
Middle Holocene

Climate change is an often-cited control on geomorphic processes in the arid southwestern United States, but links to direct climatic factors and vegetation change remain under debate. Hillslopes at a site in the eastern Mojave Desert in southern Nevada are mantled by 0–1.5 m of colluvial deposits. Accumulation of weathered bedrock combined with eolian inputs of fine sand and silt led to the formation of well-developed soil profiles. Surface sediments from both sources were incorporated into colluvium, allowing both processes to be dated with optically stimulated luminescence (OSL). OSL ages indicate a period of increased colluviation in the Late Pleistocene facilitated by enhanced bedrock weathering and dust deposition. Hillslope aspect strongly controls predominant soil environments and associated vegetation. Well-developed soils with dense grass cover extensively mantle the mesic north-aspect hillslopes, while more xeric south-aspect hillslopes are dominated by thin colluvium with minimal soil development, extensive bedrock exposure, and desertscrub vegetation. Remnants of older colluvium with moderately developed soils on south aspects, however, indicate they were once more extensively mantled by thicker colluvial deposits. The transition to drier conditions in the Holocene diminished vegetation cover on more xeric south aspects, triggering widespread erosion, whereas the more mesic north aspects retained denser grass cover that minimized erosion. The transition to drier conditions in the Holocene altered the vegetation; however, persistent perennial grass cover minimized erosion into the middle Holocene. Increasing aridity during the middle Holocene significantly reduced grass cover on more xeric south aspects, triggering erosion and alluvial deposition. OSL dates of dust incorporated into terrace sediments indicate late Middle Holocene aggradation and soil development in the Late Holocene. In contrast, maintenance of substantial perennial grass cover on mesic north aspects minimized erosion from those hillslopes throughout the Holocene.

scholarly journals New developments in the representation of Saharan dust sources in the aerosol–climate model ECHAM6-HAM2

2016 ◽  
Vol 9 (2) ◽  
pp. 765-777 ◽  
Author(s):  
Bernd Heinold ◽  
Ina Tegen ◽  
Kerstin Schepanski ◽  
Jamie R. Banks
Keyword(s):  
Climate Model ◽  
Dust Emission ◽  
Source Area ◽  
Saharan Dust ◽  
Moist Convection ◽  
Dust Source ◽  
New Developments ◽  
Infrared Imager ◽  
Dust Sources ◽  
Dust Events

Abstract. In the aerosol–climate model ECHAM6-HAM2, dust source activation (DSA) observations from Meteosat Second Generation (MSG) satellite are proposed to replace the original source area parameterization over the Sahara Desert. The new setup is tested in nudged simulations for the period 2007 to 2008. The evaluation is based on comparisons to dust emission events inferred from MSG dust index imagery, Aerosol Robotic Network (AERONET) sun photometer observations, and satellite retrievals of aerosol optical thickness (AOT).The model results agree well with AERONET measurements especially in terms of seasonal variability, and a good spatial correlation was found between model results and MSG-SEVIRI (Spinning-Enhanced Visible and InfraRed Imager) dust AOT as well as Multi-angle Imaging SpectroRadiometer (MISR) AOT. ECHAM6-HAM2 computes a more realistic geographical distribution and up to 20 % higher annual Saharan dust emissions, using the MSG-based source map. The representation of dust AOT is partly improved in the southern Sahara and Sahel. In addition, the spatial variability is increased towards a better agreement with observations depending on the season. Thus, using the MSG DSA map can help to circumvent the issue of uncertain soil input parameters.An important issue remains the need to improve the model representation of moist convection and stable nighttime conditions. Compared to sub-daily DSA information from MSG-SEVIRI and results from a regional model, ECHAM6-HAM2 notably underestimates the important fraction of morning dust events by the breakdown of the nocturnal low-level jet, while a major contribution is from afternoon-to-evening emissions.

High Latitude Dust: contemporary emissions and geomorphic interactions

2021 ◽  
Author(s):  
Joanna Bullard
Keyword(s):  
Remote Sensing ◽  
Environmental Change ◽  
High Latitude ◽  
Cold Climate ◽  
Sediment Supply ◽  
Future Research ◽  
Similar Proportion ◽  
High Latitudes ◽  
Dust Emissions ◽  
Dust Sources

&lt;div&gt; &lt;p&gt;The world&amp;#8217;s largest contemporary dust sources are in low-lying, hot, arid regions, however the processes of dust production and emission also operate in cold climate regions at high latitudes and altitudes.&amp;#160; This lecture focuses on contemporary dust emissions originating from the high latitudes (&amp;#8805;50&amp;#176;N and &amp;#8805;40&amp;#176;S) and explores three themes before setting out an integrated agenda for future research.&amp;#160; The first theme considers how much dust originates from the high latitudes and methods for determining this.&amp;#160; Estimates from field studies, remote sensing and modelling all suggest around 5% of contemporary global dust emissions originate in the high latitudes, a similar proportion to that from the USA (excluding Alaska) or Australia.&amp;#160; This estimate is a proportion of a highly uncertain figure as quantification of dust emissions from Eurasian high latitudes is limited, and the contribution of local and regional emissions (from any latitude) to the global total is thought to be considerably under-estimated.&amp;#160; Emissions are particularly likely to be under-estimated where dust sources are topographically constrained, and where cold climates reduce vertical mixing of dust plumes restricting the altitudes to which the dust can rise, because both these characteristics present particular challenges for modelling and remote sensing approaches. The second theme considers the drivers of contemporary high latitude dust emissions that reflect complex interactions among sediment supply, sediment availability and transport capacity across different geomorphic sub-systems.&amp;#160; These interactions determine the magnitude, frequency and timing of dust emissions at a range of time scales (diurnal, seasonal, decadal) but both the drivers and response can be nonlinear and hard to predict.&amp;#160; The third and final theme explores the importance of high latitude dust cycling for facilitating cross-boundary material fluxes and its impact in the atmosphere, cryosphere, and terrestrial and marine ecosystems.&amp;#160; This is influenced not only by the quantity and timing of dust emissions but also by dust properties such as particle-size and geochemistry.&amp;#160; Landscape sensitivity, spatial environmental transitions and temporal environmental change are highlighted for their importance in determining how the interactions among drivers and cycles are likely to change in response to future environmental change.&lt;/p&gt; &lt;/div&gt;

Middle Holocene environmental reconstruction and climatic inferences through multi-proxy records from Seymareh lake sediments (Zagros Mts., Iran)

2021 ◽  
Author(s):  
Michele Delchiaro ◽  
Giulia Iacobucci ◽  
Francesco Troiani ◽  
Marta Della Seta ◽  
Paolo Ballato ◽  
...  
Keyword(s):  
Sedimentation Rate ◽  
Water Discharge ◽  
Sediment Supply ◽  
Grain Size Analysis ◽  
Size Analysis ◽  
The Holocene ◽  
Middle Holocene ◽  
Lake System ◽  
Proxy Records ◽  
The Impact

&lt;p&gt;The Seymareh landslide is the largest rock slope failure (44&amp;#8201;Gm&lt;sup&gt;3&lt;/sup&gt;) ever recorded on the exposed Earth surface. It detached &amp;#8764;10&amp;#8201;ka BP from the northeastern flank of the Kabir-Kuh anticline (Zagros Mts., Iran) originating the natural dam responsible for the formation of a three-lake system (Seymareh, Jaidar, and Balmak lakes, with an area of 259, 46, and 5 km&lt;sup&gt;2&lt;/sup&gt;, respectively). The lake system persisted for &amp;#8764;3000 yr during the Holocene before its emptying phase due to overflow. A sedimentation rate of 21&amp;#8201;mm&amp;#8201;yr&lt;sup&gt;&amp;#8722;1&lt;/sup&gt; was estimated for the Seymareh lacustrine deposits, which increased during the early stage of lake emptying because of enhanced sediment yield from the lake tributaries.&amp;#160;&lt;/p&gt;&lt;p&gt;To reconstruct the climatic and environmental impact on the lake infilling, we reviewed the geomorphology of the basins and combined the results with multi-proxy records from a 30 m thick lacustrine sequence in Seymareh Lake. Major analyses comprise grain size analysis, carbon and oxygen stable isotopes of carbonate-bearing sediments, and X-ray diffraction analysis of clay minerals.&lt;/p&gt;&lt;p&gt;Lake overflowing is largely accepted as the main response to variations in water discharge and sediment supply since the alternation from dry to wet phases enhances sediment mobilization along hillslopes decreasing the accommodation space in the downstream sedimentary basins. In this regard, during the early-middle Holocene, the Seymareh area, as well as the entire Middle East, was affected by short-term climate changes at the millennial-scale, as testified by both paleoecological and archaeological evidence. Indeed, several records from Iranian lakes (i.e., Mirabad, Zeribar, Urmia) well documented the temperature and the moisture conditions of the western Zagros Mountains during the Holocene. During the early Holocene, the precipitation remained low up to 6 ka BP, reaching the driest condition around 8-8.2 ka BP. The impact of this abrupt climate change is evident across West Asia, where the first large villages with domesticated cereals and sheeps disappeared, converting to small hamlets and starting habitat-tracking. As regards the Seymareh area, a more irregular distribution of rainfalls and their increasing seasonality may support rhexistasy conditions, during which the scarce vegetation cover enhances both the hillslope erosion and sedimentation rate in the basins, most likely contributing to the overflow of Seymareh Lake.&amp;#160;&lt;/p&gt;

scholarly journals Development of a dynamic dust source map for NMME-DREAM v1.0 model based on MODIS Normalized Difference Vegetation Index (NDVI) over the Arabian Peninsula

2019 ◽  
Vol 12 (3) ◽  
pp. 979-988 ◽  
Author(s):  
Stavros Solomos ◽  
Abdelgadir Abuelgasim ◽  
Christos Spyrou ◽  
Ioannis Binietoglou ◽  
Slobodan Nickovic
Keyword(s):  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Mesoscale Model ◽  
Dust Emission ◽  
Atmospheric Model ◽  
Fine Tuning ◽  
Dust Source ◽  
Dust Sources ◽  
Modis Aod ◽  
Dynamic Source

Abstract. We developed a time-dependent dust source map for the NMME Dust Regional Atmospheric Model (DREAM v1.0) based on the satellite MODIS Normalized Difference Vegetation Index (NDVI). Areas with NDVI <0.1 are classified as active dust sources. The updated modeling system is tested for dust emission capabilities over SW Asia using a mesoscale model grid increment of 0.1∘×0.1∘ for a period of 1 year (2016). Our results indicate significant deviations in simulated aerosol optical depths (AODs) compared to the static dust source approach and general increase in dust loads over the selected domain. Comparison with MODIS AOD indicates a more realistic spatial distribution of dust in the dynamic source simulations compared to the static dust sources approach. The modeled AOD bias is improved from −0.140 to 0.083 for the case of dust events (i.e., for AOD >0.25) and from −0.933 to −0.424 for dust episodes with AOD >1. This new development can be easily applied to other time periods, models, and different areas worldwide for a local fine tuning of the parameterization and assessment of its performance.

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