Climate-vegetation dynamics in western tropical Africa: 150,000 years of past environmental change from Lake Bosumtwi (Ghana)

观测表明，热带气候区的范围对全球气候变化的敏感性超过模型预测的结果，生态调查发现森林和萨凡纳生物群落内的变化对气候变化极为敏感。然而，热带植被如何应对气候变化的动态仍然存在争议。为了探索全球气候系统和热带植被之间的关系，有必要通过已知的全球气候变化时期，例如通过冰川-间冰期循环，检查过去的植被变化记录。研究陆地植被变化的最有效方法是通过来自连续的、时间上严格限制的湖泊沉积物的化石花粉记录。然而，很少有化石花粉湖记录存在于热带地区，覆盖一个或多个完整的冰期-间冰期循环。记录过去植被变化的花粉记录在非洲的低地热带地区是特别稀缺的，只有三个记录从陆地湖泊延伸到目前的间冰期出版。1）博苏姆特维（加纳），延伸到C。28000年以前（Kyr BP），2）Barombi Mbo（喀麦隆）覆盖c。28 kyr BP，和3）Ngamakala（刚果）c.距今24万年。热带非洲的陆地植被变化是通过对几内亚湾海洋岩芯的花粉分析，通过冰川-间冰期循环推断出来的。150 kyr BP）和西北非洲的成本（>500 kyr BP; ODP 658）。然而，由于需要了解洋流、风场和沉积模式的变化，这些数据的解释变得复杂。这种数据的缺乏意味着植被对热带气候未来变化的可能反应本质上仍然是未知的。为了阐明热带植被对全球气候变化的可能反应，并提供来自热带非洲30 kyr以上陆地记录的第一批数据，我建议在两个关键的时间尺度和分辨率下研究2004年从Bosumtwi湖（加纳）提出的湖泊沉积物中的化石花粉：1）通过最后一次冰期-间冰期循环，研究植被对重大天文强迫全球气候变化事件的反应（c）。（2）在百年分辨率下，探讨植物对全球气候快速变化的响应，如Heinrich事件。

Observations indicate that the extent of the tropical climate zone is more sensitive to global climate change than model predictions suggest and ecological investigations are finding variation within both forest and savannah biomes to be extremely sensitive to climate change. However, the dynamics of how tropical vegetation responds to climate change remains controversial. To explore the relationship between the global climate system and tropical vegetation it is necessary to examine past records of vegetation change through periods of known global climate change, e.g. through glacial-interglacial cycles. The most effective way of examining terrestrial vegetation change is through fossil pollen records from continuous, and chronologically well constrained, lake sediments. However, few fossil pollen lake records exist from the tropics which cover one, or more, complete glacial-interglacial cycle. Pollen records documenting past vegetation change in the lowland tropics of Africa are particularly scarce with only three records from terrestrial lakes which extend beyond the current interglacial published. These are: 1) Bosumtwi (Ghana) which extends back c. 28 thousand calendar years Before Present (kyr BP), 2) Barombi Mbo (Cameroon) covering c. 28 kyr BP, and 3) Ngamakala (Congo) c. 24 kyr BP. Terrestrial vegetation change in tropical Africa has been inferred through glacial-interglacial cycles from pollen analysis on marine cores in the Gulf of Guinea (c. 150 kyr BP) and off the cost of north west Africa (>500 kyr BP; ODP 658). However, interpretation of these data is complicated by the need to understand changes in ocean currents, wind fields and depositional patterns. This paucity of data means that the likely nature of vegetation response to predicted future changes in tropical climate remains essentially unexplored. To shed light on the likely response of tropical vegetation to global climate change and to provide the first data from a terrestrial record in tropical Africa older than 30 kyr I propose to examine fossil pollen from lake sediments raised from Lake Bosumtwi (Ghana) in 2004 at two key time scales and resolutions: 1) to examine vegetation response to major, astronomically forced, global climate change events through the last glacial-interglacial cycle (c. 150 kyr BP) at sub-millennial resolution, and 2) to explore vegetative response to rapid global climate change, e.g. Heinrich events, during the period 30-10 kyr BP at centennial resolution.