© Graphic: Helge Arz, IOW
Schematic depiction of changes in the ocean-atmosphere system in the South Pacific in comparison, throughout the precession cycles (21,000 years).
Schematic depiction of changes in the ocean-atmosphere system in the South Pacific in comparison, throughout the precession cycles (21,000 years).
Changes in the southern westerly wind belt produce fundamental effects on the intensity and position of the Antarctic Circumpolar Current, which is the world's largest ocean current and shapes ocean circulation worldwide. In this regard, one key factor is the wind-driven upwelling of CO2-rich deep-water masses, which, due to their comparative warmth, influences both the stability of the West Antarctic Ice Sheet and the carbon budget of the Southern Ocean.
On the basis of sediment cores, the team of researchers investigated precipitation-driven changes in sediment input in the Pacific off the coast of Chile. Assessing the past 1 million years, they identified what are known as precession cycles: changes caused by natural variations in the Earth's orbital parameters; in this case, cyclical changes in the rotation of its axis that occurred roughly every 21,000 years. Changes in these and other orbital cycles are generally considered to be a major driver for the alternation between extended glacials and interglacials over the past million years.
Comment: Throughout much of Africa in recent months (from the end of August to October) exceptional rainfall and flooding has been widely reported in multiple countries as evidenced by the following headlines:
- Thousands displaced by flooding rivers in Central African Republic
- 120,000 displaced after floods in 4 regions of Ethiopia
- Death toll from Tanzania's floods and heavy rain rises to 44
- Floods trap over 100 villages in northeast Nigeria
- Mono river flooding affects 50,000 in Togo and Benin
- 8 dead after chaotic day of heavy rains, flooding in Egypt
- People feared dead after boat capsizes as flooding in Somalia forces 182,000 people from their homes
- Death toll rises to 18 in central Nigeria flood disaster - 41,000 displaced
- Unprecedented flooding affects 200,000 in South Sudan - double average rainfall for 4 weeks
- Heavy rains trigger floods in Ivory Coast
- 28 killed in floods after 8 days of torrential rain in north-eastern Ghana
- Flooding causes at least 23 fatalities in Tanzania
- Landslide kills 22 in southern Ethiopia after 10 hours of heavy rainfall
- Worst flooding in 50 years hits Niger's capital Niamey
- Algeria's capital Algiers hit with 3 months' worth of rain in 40 minutes
- West Africa: Flood death toll rises in Niger, homes destroyed in Nigeria, hundreds displaced in Chad
- Morocco floods kill 11 in bus accident
- Landslide caused by heavy rains in southern Ethiopia leaves 7 dead
- Flooding causes 2 more deaths in Morocco
- Major flooding leaves 42 dead and 5,000 homes destroyed in Niger
- At least 6 people killed by flash flood at Hell's Gate National Park, Kenya
- Floods leave at least 78 dead and 40,000 homes damaged in Sudan (UPDATE)
- Deadly floods and landslides in eastern region of Uganda
- Flooding in the south of Mauritania leaves 5 dead - nearly half the annual rainfall in a few days
- At least seven people die in flash floods in southern Morocco
All pointers to a trend of global cooling maybe?