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

热带辐合带（ITCZ）是一个有上升空气环流和大雨的地理带，有时被称为？热赤道吗?。该带是全球气候的主要大气和海洋特征，其变率主导着全球大多数人口居住的热带和亚热带气候。在海洋上空，如果ITCZ最窄和最发达，ITCZ的位置在夏季最大辐射之后季节性地在5°S和5°N之间移动。这些迁徙造成了众所周知的气候现象，如季风和季节性干旱。最近的古海洋学和古气候资料记录了过去ITCZ的大位移。在过去的3万年里，ITCZ迅速地（在几十年到几个世纪的时间内）移动，并急剧地远离其历史平均位置。在这些时间尺度上，过去的ITCZ偏移可能达到±10-15°纬度，并且（亚）热带的气候变化确实非常大。现代撒哈拉沙漠的出现就是这样一个例子，大约5000年前，这里曾经是一片水源充足、湖泊密布的地区。北非的干旱导致了北非人口的减少，尼罗河谷沿岸城市和分层文明的兴起，以及费龙文化的出现。这项工作的目的是确定ITCZ位置对高纬度全球冰量和低纬度轨道辐射强迫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可能发生的气候变化是必要的。本项目将资助一名博士后研究员和一名来自代表性不足群体的本科生研究助理。

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.