Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum

Abstract

Palaeo-dust records in sediments and ice cores show that wind-borne mineral aerosol ('dust') is strongly linked with climate state. During glacial climate stages, for example, the world was much dustier, with dust fluxes two to five times greater than in interglacial stages. However, the influence of dust on climate remains a poorly quantified and actively changing element of the Earth's climate system. Dust can influence climate directly, by the scattering and absorption of solar and terrestrial radiation, and indirectly, by modifying cloud properties. Dust transported to the oceans can also affect climate via ocean fertilization in those regions of the world's oceans where macronutrients like nitrate are abundant but primary production and nitrogen fixation are limited by iron scarcity. Dust containing iron, as fine-grained iron oxides/oxyhydroxides and/or within clay minerals, and other essential micronutrients (e.g. silica) may modulate the uptake of carbon in marine ecosystems and, in turn, the atmospheric concentration of CO2. Here, in order to critically examine past fluxes and possible climate impacts of dust in general and iron-bearing dust in particular, we consider present day sources and properties of dust, synthesise available records of dust deposition at the last glacial maximum (LGM); evaluate the evidence for changes in ocean palaeo-productivity associated with, and possibly caused by, changes in aeolian flux to the oceans at the LGM; and consider the radiative forcing effects of increased LGM dust loadings.

Enhanced primary productivity and magnetotactic bacterial production in response to middle Eocene warming in the Neo-Tethys Ocean

“…Maher et al, 2010;Roberts et al, 2011;Larrasoaña et al, 2012;Liu et al, 2012). Roberts et al (2011) reported enhanced iron supply by aeolian dust in Eocene sediments (ODP Hole 738B) of the southern Kerguelen Plateau (Indian Ocean), where a marked increase in hematite concentrations coincided with a switch from oligotrophic to eutrophic conditions.…”

Strengthening of North American dust sources during the late Pliocene (2.7 Ma)

“…Globally distributed climate records show that the global emission of dust was significantly higher during the most recent glacials than during interglacials such as the present (e.g., Maher et al, 2010;Mahowald et al, 2011;McGee et al, 2010). For example the analysis of dust particles in ice cores from the Antarctic continent shows that throughout the last 800 ka the dust flux to Antarctica was 25 times higher during glacials than during interglacials (Lambert et al, 2008).…”

“…This heterogeneous mixture of aerosols, i.e. dust, plays an important role in global climate (Maher et al, 2010) as it influences the radiative forcing of the atmosphere (Mahowald et al, 2006b), and can be a source of nutrients (e.g., iron) to the open ocean that can lead to a strengthening of the biological pump (Fung et al, 2000;Martin, 1990;Mills et al, 2004). In addition, dust particles influence cloud formation by providing cloud condensation nuclei (Mahowald and Kiehl, 2003), and can affect the albedo of ice sheets (Ridgwell, 2002).…”

Trace elements and metal pollution in aerosols at an alpine site, New Zealand: Sources, concentrations and implications

“…The role of dust in sedimentary systems is apparent in oceanic settings remote from continents where significant dust mantles the ocean floor (Hesse, 1994;McGee et al, 2007;Rea, 1994). Copious dust transport and deposition marked the glacial cycles of the Quaternary Period, resulting in accumulation of loess downwind of cold climate regions, most notably in China where loess deposits of up to 100 m date from this time, but also in Eurasia, North America, Northern Europe, southern South America and New Zealand (Maher et al, 2010). Dust therefore played a major role in biogeochemical processes during cold climate phases.…”