Chinese Loess Plateau
One of the most valuable climate archives in the world is the Chinese Loess Plateau which covers an area of approximately 640,000 km2 and contains a 22 Million years (Ma) record of highly resolved dust deposition and climate proxies. It is an ideal area to study long term and abrupt change in dust deposition and is influenced by multiple climate systems as well as uplift of large mountain belts and the Tibetan Plateau.
Fig. 1. View of Luochuan.
Why study dust?
Dust storms can form in dry (arid) regions around the world like the Sahara, or in parts of the USA. The storm often drives dust into the atmosphere, as shown in the sketch below, which can have a large impact on climate and on human health.
Figure 1. redrawn from Pye & Zhou 1989 showing dust transport mechanisms.
There are several studies which focus on modern dust, including one by NASA which has really good atmospheric dust animations showing how dust can move around the globe.
How can dust affect climate?
Dust can change the atmospheric radiation budgets. Most of the energy which affects the Earth's temperature and weather comes from the Sun. the atmospheric radiation budget is the balance between the amount of the Sun's energy that is reflected or absorbed by the Earth. Clouds and dust in the atmosphere can reflect the Sun's energy back into space causing lower surface temperatures.
It can also change ocean productivity. Dust deposited into oceans can deliver extra nutrients (phosphorous, silicon and iron) into the upper part of the sea. This encourages the growth of oceanic phytoplankton which can increase CO2 uptake in some ocean regions and reduce concentrations in the atmosphere. As CO2 is a greenhouse gas this directly impacts global climate.
Dust, key to past climate change?
Dust deposits have also been studied to provide information about past climate change. Loess is the accumulation of dust and variations within the properties of the loess deposits reflects past climate changes.
For example within the loess dust deposits studied in this project there are layers of soil. These loess and soil layers can be correlated to glacial and inter-glacial periods and then to the marine oxygen isotope record to provide information about past climate, as shown in the diagram cartoon to the left. Fig. 2 shows loess and soil layers at Baode which transition into red clay layers, the boundary of which lies at about 2.6 Ma.
Although many studies have been undertaken on modern dust, the role of abrupt and long-term changes in atmospheric dust source in past climate change is not well understood and is one of the main aims for this project.
Fig. 2. Baode stratigraphy.
Pye, K. & Zhou, L.P. 1989. Late Pleistocene and Holocene aeolian dust deposition in north China and the northwest Pacific Ocean. Palaeogeography, Palaeoclimatology, Palaeoecology, 73, 11-23.
Sampling the loess plateau at Beiguoyuan.