Temporal variability of dust deposition from Holocene lake sediment records in the San Juan Mountains, CO.
Abstract
The southwest is the driest and dustiest region of the contiguous U.S. and millions of stakeholders rely on snowmelt from the San Juan Mountains of Colorado. Dust on snow accelerates spring snowmelt; however, the long-term baseline and natural variability of regional dust fluxes are poorly constrained, presenting a challenge to water managers. As drought and dustiness are projected to worsen in the future, establishing a baseline of past dust deposition in the San Juan Mountains becomes essential for management decisions.
Dust reconstructions were developed from sediment cores from three lakes in the San Juan Mountains to investigate temporal patterns of dust deposition over the Common Era (the last 2000 years) and over the last 15,000 years. Monte-Carlo end-member analysis of grain-size and elemental composition, which incorporates measurement and model uncertainties, was combined with age uncertainty through GeochronR. This novel Bayesian approach was used to calculate dust mass accumulation rates for each lake and to combine records taking into account analytical and age uncertainty, providing the first all-encompassing estimate of dust deposition flux for this region. The Common Era records are in agreement but show little relation between periods of lasting drought (e.g. during the Medieval and Roman periods) and dust mass accumulation rates. This indicates other processes in the dust cycle as well in the lake catchments play an important role in mediating dust accumulation. Following the arrival of Europeans to the Southwest ( 1500 A.D.) dust deposition increased by 150-200%. Put into a longer-term context, human induced dustiness represents the highest interval of dust flux in the Holocene. This has serious implications for land-use management, as the records signify human activities have a greater impact on the dust cycle in this region than natural processes alone.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFMPP43C1950A
- Keywords:
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- 3305 Climate change and variability;
- ATMOSPHERIC PROCESSESDE: 1620 Climate dynamics;
- GLOBAL CHANGEDE: 1630 Impacts of global change;
- GLOBAL CHANGEDE: 4928 Global climate models;
- PALEOCEANOGRAPHY