High and Low-Latitude Controls on the Mean Position of the Atlantic ITCZ (0-150 ka BP)

热带辐合带(ITCZ)是一个上升的空气环流和暴雨的地理带，有时被称为热赤道。这一地带是全球气候的主要大气和海洋特征，其变异性主导着大多数全球人口居住的热带和亚热带的气候。在ITCZ最窄和最发育的大洋上，ITCZ的位置在夏季辐射最大后季节性地在5°S到5°N之间移动。这些迁徙是众所周知的气候现象，如季风和季节性干旱的原因。最近的古海洋学和古气候数据记录了过去ITCZ的大量漂移。在过去的3万年里，ITCZ迅速(在几十年到几个世纪内)发生了变化，并戏剧性地偏离了其历史平均位置。过去ITCZ在这些时间尺度上的漂移可能高达±10-15°纬度，(亚)热带的气候变化确实很大。现代撒哈拉沙漠的出现就是这样一个例子，它大约有5000年的历史，而以前是一个灌溉良好、湖泊遍布的地形。北非的这种干旱导致了北非人口的减少，尼罗河流域城市分层文明的兴起，以及幻影文化的出现。这项工作的目的是确定ITCZ位置对高纬度全球冰量和低纬轨道辐射强迫的已知变化的相对敏感性。了解ITCZ对已知的自然气候变化的敏感性对于估计未来全球变暖中可能发生的气候变化是必要的。该项目的资金将支持来自代表性不足群体的一名博士后研究员和本科生研究助理。

The ITCZ (Intertropical Convergence Zone) is a geographic band with ascendant air circulation and heavy rain, sometimes referred to as the ?thermal equator?. This zone is a dominant atmospheric and oceanic feature of global climate, and its variability dominates the climate of the tropics and subtropics where most of the global population lives. Over the oceans, where it the ITCZ is narrowest and best developed, the position of the ITCZ moves seasonally between 5°S and 5°N following the maximum summer season radiation. These migrations are responsible for well-known climate phenomenon such as monsoons and seasonal droughts. Recent paleoceanographic and paleoclimate data have documented large excursions of the ITCZ in the past. Over the last 30,000 years the ITCZ has shifted rapidly (within decades to centuries) and dramatically away from its historical mean position. Past ITCZ excursions over these timescales may have been as large as ±10-15° latitude, and the climate changes in the (sub)tropics were very large indeed. The emergence of the modern day Saharan desert roughly 5,000 years age from what was previously a well-watered, lake-filled terrain is one such example. This drying of North African led to the depopulation of North Africa, and the rise of urban, stratified civilizations along the Nile Valley and the emergence of Phaeronic culture.The objective of this work is to determine the relative sensitivity of the ITCZ position to known changes in high-latitude global ice volume and low-latitude orbital radiation forcing. Understanding sensitivity of ITCZ to known, natural climate changes is necessary to estimate possible future climate changes in a warming world. Funding of this project will support a post-doctoral researcher and undergraduate research assistants from underrepresented groups.