Global Climate Cycles

Level M (Master of Science) module: powerpoint lectures and a number of practical

Palaeoclimate Change

Level 3 (BSc) module with lectures and practical

Deep Ocean Carbonate Chemistry and Glacial-Interglacial Atmospheric CO₂ Changes

Changes in deep ocean carbonate chemistry have profound implications for glacial-interglacial atmospheric CO₂ changes. Here, we review deep ocean carbonate ion concentration ([CO₃²⁻]) changes based on the benthic foraminiferal boron-to-calcium ratio (B/Ca) and their links to global carbon reorganization since the last ice age. Existing deep ocean [CO₃²⁻] reconstructions are consistent with changes in the biological pump, in ocean stratification, and in the associated oceanic alkalinity inventory as key mechanisms for modulating atmospheric CO₂ on glacial-interglacial time scales. We find that the global mean deep ocean [CO₃²⁻] was roughly similar between the Last Glacial Maximum (LGM; 18,000–22,000 years ago) and the Late Holocene (0–5,000 years ago). In view of elevated glacial surface [CO₃²⁻], this indicates enhanced storage of respiratory carbon in a more alkaline deep ocean during the LGM. During early deglaciation, rising [CO₃²⁻] at three locations in the deep ocean suggests a release of deep-sea CO₂ to the atmosphere, probably via the Southern Ocean. Both increased late deglacial carbonate burial in deep-sea sediments due to elevated [CO₃²⁻] and Holocene expansion of coral reefs on newly flooded continental shelves depleted global ocean alkalinity, which reduced CO₂ solubility in seawater and contributed to atmospheric CO₂ rises at these times

Dynamics of Green Sahara Periods and Their Role in Hominin Evolution

Astronomically forced insolation changes have driven monsoon dynamics and recurrent humid episodes in North Africa, resulting in green Sahara Periods (GSPs) with savannah expansion throughout most of the desert. Despite their potential for expanding the area of prime hominin habitats and favouring out-of-Africa dispersals, GSPs have not been incorporated into the narrative of hominin evolution due to poor knowledge of their timing, dynamics and landscape composition at evolutionary timescales. We present a compilation of continental and marine paleoenvironmental records from within and around North Africa, which enables identification of over 230 GSPs within the last 8 million years. By combining the main climatological determinants of woody cover in tropical Africa with paleoenvironmental and paleoclimatic data for representative (Holocene and Eemian) GSPs, we estimate precipitation regimes and habitat distributions during GSPs. Their chronology is consistent with the ages of Saharan archeological and fossil hominin sites. Each GSP took 2-3 kyr to develop, peaked over 4-8 kyr, biogeographically connected the African tropics to African and Eurasian mid latitudes, and ended within 2-3 kyr, which resulted in rapid habitat fragmentation. We argue that the well-dated succession of GSPs presented here may have played an important role in migration and evolution of hominins

Warfare in Late Neolithic\Early Chalcolithic Pisidia, southwestern Turkey. Climate induced social unrest in the late 7th millennium calBC

This paper proposes an association between climate forcing connected with the 8200 calBP ‘climate event’ and a postulated phase of internecine warfare and population collapse at Late Neolithic/Early Chalcolithic sites in Pisidia, southwestern Turkey. A summary of this evidence is provided and a hypothetical scenario considered in the context of contemporaneous developments in neighbouring regions

Appreciation of peer reviewers for 2015

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/133577/1/rog20102.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/133577/2/rog20102_am.pd

A geological perspective on potential future sea-level rise

During ice-age cycles, continental ice volume kept pace with slow, multi-millennial scale, changes in climate forcing. Today, rapid greenhouse gas (GHG) increases have outpaced ice-volume responses, likely committing us to > 9 m of long-term sea-level ri

Dimensional analysis identifies contrasting dynamics of past climate states and critical transitions

While one can unequivocally identify past climate transitions, we lack comprehensive knowledge about their underlying mechanisms and timescales. Our study employs a dimensional analysis of benthic stable isotope records to uncover, across different timescales, how the climatic fluctuation of the Cenozoic are associated with changes in the number of effective degrees of freedom. Precession timescales dominate the Hothouse and Warmhouse states, while the Icehouse climate is primarily influenced by obliquity and eccentricity timescales. Notably, the Coolhouse state lacks dominant timescales. Our analysis proves effective in objectively identifying abrupt climate shifts and extremes. This is also demonstrated using high-resolution data from the last glacial cycle, revealing abrupt climate shifts within a single climate state. These findings significantly impact our understanding of the inherent stability of each climate state and the evaluation of (paleo-)climate models' ability to replicate key features of past/future climate states and transitions

Thank You to Our 2018 Peer Reviewers

On behalf of the authors and readers of Reviews of Geophysics, the American Geophysical Union (AGU), and the broader scientific community, the Editors wish to wholeheartedly thank those who reviewed the manuscripts for Reviews of Geophysics in 2018. Reviews of Geophysics is the top rated journal in Geophysics and Geochemistry and it could not exist without your investment of time and effort, lending your expertise to ensure that the papers published in this journal meet the standards that the research community expects for it. We sincerely appreciate the time spent reading and commenting on manuscripts, and we are very grateful for your willingness and readiness to serve in this role. Reviews of Geophysics published 20 review papers and an editorial in 2018, covering most of the AGU Section topics, and for this we were able to rely on the efforts of 85 dedicated reviewers from 20 countries. Many reviewers answered the call multiple times. Thank you again. We look forward to a 2019 of exciting advances in the field and communicating those advances to our community and to the broader public