Here is a preprint for our forthcoming chapter in the Encyclopedia of Climate System Science. Our perspective is that ice sheet, ocean circulation and global carbon cycle are critical to the development of ice ages, which are not simply caused by changes in Earth’s orbit as Milankovitch would have it.
Here is a preprint for our forthcoming chapter in the Encyclopedia of Climate System Science. Our perspective is that ice sheet, ocean circulation and global carbon cycle are critical to the development of ice ages, which are not simply caused by changes in Earth’s orbit as Milankovitch would have it.
Radiocarbon (14C) is produced in the atmosphere and spreads through the surface carbon cycle before, you guessed it, radioactive decay. Hence the name, radiocarbon. In contrast, carbon spit out from Earth’s interior is 14C-free and can thus produce a “negative 14C anomaly” in the region of release. Working with Pat Rafter at USF and my former PhD student Ryan Green (now at Equatic), we reconstruct and simulate a major 14C anomaly in the Gulf of California.
We find two main pulses of maybe 800PgC total carbon release during the end of the last ice age, but smaller 14C anomalies persist to the modern day. We also find that the carbon release did not cause ocean acidification or significantly increase CO2, because it was neutralized by a equimolar pulse of alkalinity release to the ocean. Our results lead us to conclude that this highly unusual instance of large scale neutralized-carbon release could be an important geologic analogue for Ocean Alkalinity Enhancement (OAE) as means for marine Carbon Dioxide Removal (mCDR) in the ongoing challenge to mitigate anthropogenic climate change and ocean acidification.
Our four papers on the topic (left to right): (1) detailed reconstructions of deglacial 14C anomalies in the Gulf of California, (2) global carbon cycle constraints on geologic carbon release during the deglacial period, (3) mass balance and pH constraints in simulating regional impacts of carbon release, and (4) regional assessment of 14C anomalies since the last ice age. This inferred release of neutralized carbon remains a challenge to our current paradigm of the global carbon cycle, but it does not significantly affect our understanding of the ice age carbon cycle or our ability to reconstruct ocean circulation using 14C.
Today I was interviewed by Mira Shah of carbon economics on her Signals of Change podcast. Mira had questions about our carbon cycle research and how it may inform sustainable management of the environment going forward.
Dr. Ryan Green just had a second manuscript accepted for publication, where we argue that the large-scale release of geologic carbon at the end of the last ice age is likely responsible for radiocarbon (14C) anomalies discovered in the Gulf of California region. Unlike any previous work, we argue that the carbon was released with and neutralized by alkalinity so as not to cause ocean acidification or atmospheric CO2 increase.
A new study led by Simone Moretti (MPIC) suggest there could be a general mechanism speeding up deep ocean circulation and raising atmospheric CO2, thereby producing a positive feedback. This mechanism is thought to help explain ice ages, but the new study now provides evidence it might have also amplified the warmest conditions of the Eocene hot-house climate.
In a new chapter for the third edition of the Treatise on Geochemistry with Kat Allen and Sandy Kirtland Turner, we systematically analyze the dynamics that couple climate and carbon cycle through CO2 radiative forcing. This includes the first analytical derivation of the silicate weathering timescale. The relevant context of proxy systems for climate and carbon cycle and terminology for coupled climate-carbon cycle change is intended to introduce Earth System science.
Ryan Green defended his PhD dissertation on natural neutralized carbon release and how anthropogenic carbon might be neutralized by releasing additional alkalinity to the ocean. Dr. Green’s first paper on the topic was published in 2024 and his second is hot on the heels. Congratulations!
In a perspective on Quaternary climate change with Tom Chalk, published in the Encylopedia of Quaternary Science, we question the conventional wisdom that ice ages result from regular changes in Earth’s orbit or some other purely physical mechanism. We argue instead that the global carbon cycle and greenhouse gasses need to be included as a cause of climate change.
In a new synthesis review with Danny Sigman, published in the Oxford Research Encyclopedia of Climate Science, we entertain the possibility that changes in the ocean’s biological pump and alkalinity were the dominant driver of CO2 and global climate change during Pleistocene ice ages. We show that land-carbon changes effects were canceled by ocean carbonate compensation, and that ice sheet and temperature changes cancel each other. The effect of deep ocean carbon storage, in contrast, is amplified by carbonate compensation, yielding durable CO2 changes.
Terra’s research so far has focused on gradual changes in seawater chemistry unfolding over geologic deep time, and their effects on the global carbon cycle simulated with the cGENIE Earth System Model. For her ARCS proposal Terra will use her model skills and chemistry expertise to investigate how the effect of many concurrent ‘negative emission’ interventions add up in countering anthropogenic atmospheric CO2 rise and climate change. Congrats Terra!
