1 / 26

Overview

African Monsoon Variability over Past Millennia Peter B. deMenocal Jennifer Arbuszewski Jess Adkins Zhengyu Liu. Overview. The African monsoon and orbital forcing The early Holocene African Humid Period Climate model simulations: … mechanisms for abrupt change. Giannini et al. (2003).

rivka
Download Presentation

Overview

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. African Monsoon Variability over Past MillenniaPeter B. deMenocal Jennifer Arbuszewski Jess Adkins Zhengyu Liu

  2. Overview The African monsoon and orbital forcing The early Holocene African Humid Period Climate model simulations: … mechanisms for abrupt change

  3. Giannini et al. (2003) Sahel Drought (1960s onward)

  4. Cool SSTs Maximum upwelling Steep thermocline slope The African Monsoon and Tropical Atlantic Upwelling W. Ruddiman, “Earth's Climate Past and Future”

  5. Orbital Precession and the MonsoonKutzbach (1981) W. Ruddiman, “Earth's Climate Past and Future”

  6. Linear (?) monsoon sensitivity

  7. Precessional monsoon variability Med. Sapropels Tropical Upwelling African Climate (McIntyre et al., 1989; Molfino and McIntyre, 1993; Pokras and Mix, 1985; Rossignol-Strick, 1983)

  8. …persisted for millions of years! Miocene Mediterranean Sapropels (Sicily; Frits Hilgen)

  9. NW African dust export Site 658

  10. African Humid Period AHP deMenocal et al., 2000

  11. African Humid Period Africa was much wetter between ca. 15-5 kyr BP. Most of Saharan Desert vegetated, wetland fauna.

  12. North Africa wet during early Holocene Paleolake sediments in Mali (NW Africa)

  13. Climate-Controlled Occupation of the Eastern Sahara Kuper and Kroepelin, 2006

  14. Faiyum Mirimde Egyptian Neolithic (6.5-4.5 ka BP) Badari Nagada

  15. AHP: A pan-North African event Liu et al., 2007

  16. Albedo-Vegetation feedback? Claussen et al., 1999; deMenocal et al., 2000

  17. Fully coupled transient O-A-Veg GCM Liu et al. (QSR in press)

  18. Climate Model insight African climate very sensitive to orbital radiation changes. Abrupt responses to gradual forcing due to some aspect of vegetation feedback. Humid-arid transitions occurred within centuries. SST influence uncertain but present in historical records.

  19. Annual sea-surface temperature Annual Evap - Precip

  20. Change in P-E (m/yr) Change in surface temperature (°C) Meridional ITZ displacements:LGM water-hosing experiments Vellinga and Wood (2002)

  21. LGM Collapse of zonal SST Gradient

  22. SST gradients along transect

  23. Fresh Large and abrupt Deglacial ITCZ Swings Salty

  24. Summary Past African climate changes were large. Moisture budget changes were abrupt. Likely importance of vegetation feedbacks, perhaps SSTs as well.

More Related