Increased Dust Deposition in the Pacific Southern Ocean During Glacial Periods

Abstract

Dust deposition in the Southern Ocean constitutes a critical modulator of past global climate variability, but how it has varied temporally and geographically is underdetermined. Here, we present data sets of glacial-interglacial dust-supply cycles from the largest Southern Ocean sector, the polar South Pacific, indicating three times higher dust deposition during glacial periods than during interglacials for the past million years. Although the most likely dust source for the South Pacific is Australia and New Zealand, the glacial-interglacial pattern and timing of lithogenic sediment deposition is similar to dust records from Antarctica and the South Atlantic dominated by Patagonian sources. These similarities imply large-scale common climate forcings, such as latitudinal shifts of the southern westerlies and regionally enhanced glaciogenic dust mobilization in New Zealand and Patagonia.

Simulation of climate, ice sheets and CO<sub>2</sub> evolution during the last four glacial cycles with an Earth system model of intermediate complexity

“…Such choice is supported by the recent measurements of iron content in Southern Ocean sediment cores (Lamy et al, 2014). In the fully interactive run, the iron flux over the Southern Ocean (D) in arbitrary units is parameterised through the global sea level change as D = 100 dS dt + 10 max(S − 50; 0) + 1.5S, where S is the ice volume expressed in metres of sea level equivalent and time t is in years.…”

Sea ice led to poleward-shifted winds at the Last Glacial Maximum: the influence of state dependency on CMIP5 and PMIP3 models

“…Iron-rich dust borne by Southern Hemisphere winds is thought to increase Southern Ocean productivity (Kohfeld et al, 2005). Lamy et al (2014) show that large-scale southern hemispheric climate forcings, likely wind related, enhanced cold glacial period dust mobilisation in Australia, New Zealand, and Patagonia. Ferrari et al (2014) hypothesise a Southern Ocean dividing latitude between negative and positive buoyancy forcing at the edge of the summer sea ice edge, with knock-on impacts for ocean dynamics.…”

Climate engineering by mimicking natural dust climate control: the iron salt aerosol method

“…The windblown dust and its iron content effect on marine productivity in the Southern Ocean is thought to be a key determinant of atmospheric CO 2 concentrations (Maher and Dennis, 2001). During high dust level periods, the global average temperature fell to 10 • C (Lamy et al, 2014;Martin, 1990;Martínez-Garcia et al, 2011), which is 4.5 • C lower than the current global average temperature. Loess sediments in the Northern and Southern Hemisphere on continents and ocean floors originate from these cold dusty periods.…”

“…Dust deposition in the Southern Ocean during glacial periods was 3 to 10 times greater than during interglacial periods, and its major source region was probably Australia or New Zealand (Lamy et al, 2014). The windblown dust and its iron content effect on marine productivity in the Southern Ocean is thought to be a key determinant of atmospheric CO 2 concentrations (Maher and Dennis, 2001).…”

“…Meanwhile, more evidence has accumulated that mineral dust was a main factor in the cause of the cold periods and that the iron (Fe) fraction of windblown dust aerosol fertilized the oceans' phytoplankton, activating the assimilative conversion of CO 2 into organic carbon Lamy et al, 2014;Maher et al, 2010;Martin, 1990;Martínez-García et al, 2014;Ziegler et al, 2013) and carbonate, which composes the main dry-body substance of phytoplankton, together with silica, another component of dust (Tréguer and Pondaven, 2000).…”