Nav: Home

Plankton as a climate driver instead of the sun?

May 22, 2019

The climate history of the earth is marked by periodic changes that are usually ascribed to the solar radiation reaching the surface of the earth. This insolation is not constant over geological time but modulated by cyclic changes in the earth's orbital parameters. One of the key parameters affecting insolation is the tilt of the earth's rotation axis (obliquity) that changes periodically over time with a cycle length of about 40 000 years. Chemical and isotopic signatures of sediments that were deposited during the Cretaceous and other periods of earth's history document regular changes in temperature and carbon cycling on this time scale. The 40 kyr cycles observed in the geological climate archives are believed to be the result of obliquity-triggered insolation changes affecting the surface temperature, the circulation of ocean and atmosphere, the hydrological cycle, the biosphere, and ultimately the carbon cycle. One of the problems with this standard theory is that changes in global insolation are very small and have to be amplified by poorly understood positive feedback mechanisms to affect global climate.

A group of scientists from Kiel, Germany propose a very different perspective that emerges from a new numerical model of the marine biosphere. It simulates the turnover of plankton biomass in the ocean and resolves the associated microbial oxidation and reduction reactions controlling the standing stocks of dissolved oxygen, sulfide, nutrients and plankton in the ocean. In their model experiments the scientists found surprisingly a self-sustained 40 kyr climate cycle using the biogeochemical model integrated in a circulation model of the Cretaceous Ocean without applying obliquity forcing.

"In our model, the carbon cycle is largely controlled by plankton living in the surface ocean", explains Prof. Dr. Klaus Wallmann from GEOMAR, lead author of the study which was recently published in Nature Geoscience. Plankton consumes atmospheric CO2 via photosynthesis and by microorganisms that degraded plankton biomass and release CO2 back into the atmosphere. Since CO2 is a potent greenhouse gas, the biological CO2 turnover affects surface temperatures and global climate. The growth of plankton is controlled by nutrients that take part in a range of microbial oxidation and reduction reactions.

"We have integrated this new biogeochemical model in a circulation model of the Cretaceous Ocean, and it creates a self-sustained 40 kyr climate cycle without applying obliquity forcing", says Dr. Sascha Flögel, co-author from GEOMAR. "From our perspective, the cycle is induced by a web of positive and negative feedbacks that are rooted in the oxygen-dependent turnover of nitrogen, phosphorus, iron and sulfur in the ocean. Chemical and isotopic data recorded in sediments deposited in the Cretaceous Ocean show periodic changes that are consistent with the model results", Flögel continues

In this new view on climate change, the relationship between causes and effects is radically different from the standard orbital theory. The marine biosphere rather than insolation is setting the pace and amplitude by controlling the partial pressure of CO2 in the atmosphere. "Our new theory is supported by observations and consistent with our understanding of biogeochemical cycles in the ocean", according to Prof. Wallmann.

"However obliquity and other orbital parameters may also affect global climate change when their delicate effects on insolation are amplified by positive feedback mechanisms. Therefore, the periodic climate change documented in the geological record may reflect both the breath of the biosphere and the response of the earth system to external orbital and insolation forcing", summarizes Prof. Dr. Wolfgang Kuhnt from Kiel University who participated in this study.
-end-


Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Related Climate Change Articles:

The black forest and climate change
Silver and Douglas firs could replace Norway spruce in the long run due to their greater resistance to droughts.
For some US counties, climate change will be particularly costly
A highly granular assessment of the impacts of climate change on the US economy suggests that each 1°Celsius increase in temperature will cost 1.2 percent of the country's gross domestic product, on average.
Climate change label leads to climate science acceptance
A new Cornell University study finds that labels matter when it comes to acceptance of climate science.
Was that climate change?
A new four-step 'framework' aims to test the contribution of climate change to record-setting extreme weather events.
It's more than just climate change
Accurately modeling climate change and interactive human factors -- including inequality, consumption, and population -- is essential for the effective science-based policies and measures needed to benefit and sustain current and future generations.
Climate change scientists should think more about sex
Climate change can have a different impact on male and female fish, shellfish and other marine animals, with widespread implications for the future of marine life and the production of seafood.
Climate change prompts Alaska fish to change breeding behavior
A new University of Washington study finds that one of Alaska's most abundant freshwater fish species is altering its breeding patterns in response to climate change, which could impact the ecology of northern lakes that already acutely feel the effects of a changing climate.
Uncertainties related to climate engineering limit its use in curbing climate change
Climate engineering refers to the systematic, large-scale modification of the environment using various climate intervention techniques.
Public holds polarized views about climate change and trust in climate scientists
There are gaping divisions in Americans' views across every dimension of the climate debate, including causes and cures for climate change and trust in climate scientists and their research, according to a new Pew Research Center survey.
The psychology behind climate change denial
In a new thesis in psychology, Kirsti Jylhä at Uppsala University has studied the psychology behind climate change denial.

Related Climate Change Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#529 Do You Really Want to Find Out Who's Your Daddy?
At least some of you by now have probably spit into a tube and mailed it off to find out who your closest relatives are, where you might be from, and what terrible diseases might await you. But what exactly did you find out? And what did you give away? In this live panel at Awesome Con we bring in science writer Tina Saey to talk about all her DNA testing, and bioethicist Debra Mathews, to determine whether Tina should have done it at all. Related links: What FamilyTreeDNA sharing genetic data with police means for you Crime solvers embraced...