Abstract
Dust concentrations in Greenland ice show pronounced glacial/interglacial variations with almost two orders of magnitude increase during the Last Glacial Maximum. Greenland glacial dust was previously sourced to two East Asian deserts: the Taklimakan and Gobi deserts. Here we report the first high-resolution Pb and Sr isotopic evidence for a significant Saharan dust influence in Greenland during the last glacial period, back to ~31 kyr ago, from the Greenland NEEM ice core. We find that during Greenland Stadials 3–5.1 (~31 to 23 kyr ago), the primary dust provenance was East Asia, as previously proposed. Subsequently, the Saharan isotopic signals emerge during Greenland Stadials 2.1a–2.1c (~22.6 to 14.7 kyr ago) and from the late Bølling-Allerød to the Younger Dryas periods (~13.6 to 12 kyr ago), coincident with increased aridity in the Sahara and efficient northward transport of dust during these cold periods. A mixing isotopic model proposes the Sahara as an important source, accounting for contribution to Greenland glacial dust of up to 50%, particularly during Greenland Stadial 2.1b and the late Bølling-Allerød to the Younger Dryas periods. Our findings provide new insights into climate-related dust provenance changes and essential paleoclimatic constraints on dust-climate feedbacks in northern high latitudes.
Highlights
Atmospheric mineral dust is an important component of the Earth’s climate system, potentially affecting the radiative balance through reflection and absorption of both the incoming solar radiation and the outgoing infrared radiation[1,2]
The Last Glacial Maximum (LGM) is well characterized by its very dust-laden atmosphere, as reflected by an approximate 20-fold increase in Greenland dust deposition compared to the Holocene[10] potentially caused by the expansion of source areas, enhanced dust mobilization by strong winds, and increased atmospheric residence time[11,12]
The isotopic data were obtained in 67 sections from the 2,540-m-long North Greenland Eemian Ice Drilling (NEEM) ice core (77.45° N, 51.06° W, altitude 2,450 m above sea level)[24] with ages ranging from ~8,260 to ~30,800 years before present
Summary
We report the first high-resolution Pb and Sr isotopic records evidencing Saharan dust inputs to Greenland during certain periods of the late last glacial age (LLGA). The distinct isotopic signatures for Saharan dust emerge in the 87Sr/86Sr versus 206Pb/207Pb plot for the samples corresponding to the late B/A and YD periods (Supplementary Fig. S3b), providing insights into climatic conditions favoring dust transport out of the Sahara to Greenland. The Saharan contribution exhibits a decline during the B/A warm period and subsequent enhancement from the late B/A to the YD cold period (Fig. 4a) This feature matches well with changes in Greenland dust concentrations and Saharan dust deposition in the tropical North Atlantic that are synchronous with the humid phase of the Sahara, initially commenced at ~15 kyr BP, and the following aridity punctuated by the YD40, and the African Humid Period around ~12.3–5.5 kyr BP40–42 (Fig. 4b–e). Further studies, extending back to the full glacial period (~100 kyr BP), will provide new insights into climate-related changes in dust provenance, transport mechanisms and vertical dust distribution patterns in northern high latitudes, and the resultant climate feedback processes, linked to the past Arctic amplification over the full glacial age
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