Climate research – on the left in the cold

It is quite rare that individual living things are mentioned in newspapers and magazines or even in the science program of television. If at all, then it is usually a pathogen. But since people have taken care of the climate and interested in how the climate and environmental conditions have changed in the past, the tiny people of the World Ocean have been taken into account more than before. On the one hand, because they are climate-relevant themselves due to their massive metabolism, on the other hand because some of them are used as climate data storage.

An animal group has caused a sensation in this capacity. “Every second or third report on the Paleoclima calls their-as it should be for a star-sounding names: they are foraminiferen,” said Andreas Mackensen when I once visited him in the Alfred Wegener Institute for Polar and Marine Research (AWI) in Bremerhaven. They have been inhabilizing the sea floors since the Erdaltism and the upper layers of water in the World Ocean since the middle of the Jura period. More than 40,000 species are known from the history of the earth. Around 4,000 species live in today’s seas, again only 40 planktically, that is, in the upper pair of hundred meters of the water column. Most of them are limestone scales, and what the whimsical is: they build, figuratively speaking, the environmental conditions into their housing. Even what types occur where and how they design their body, says something about the respective climate.

Mackensen mentions a certain species as an example, which builds their spirally arranged chamber housing in the cold water on the left, in warmer waters on the right. It no longer lives for more than a year, then the lime shell sinks to the ground. If an expedition team wins a sediment core with dung pipes or so -called box lodges, the relics from the individual layers are isolated, and solely on the basis of the rotation of the spiral, on the right – left, can be seen: during this time the water was colder or warmer.

Building material from the water

Foraminifers are therefore signal carriers. The animals install climate formation into their protective cover, so to speak. How can you imagine that? The housing are made of calcium carbonate (Caco₃). The word stem Foraminiferen already says a lot about these unicellular organisms: “Foramen” means wearing hole and “ferre” in Latin. They are “holes”. Because the cell grows, it always builds new chambers in a spiral arrangement, and these chambers have openings or holes with each other.

The building material is elements from the water, and this takes advantage of the isotope analysis. “A charming, strong tool,” says my current conversation partner Lester Lembke-Jene, Mariner Geologist at the AWI. “In the meantime, we can analyze some of these millimeter small housings using always refined methods and the statements go back more than 60 million years.” He pulls a slide on with hundreds of vials: samples from a sediment core that are prepared for the isotope analysis in the mass spectrometer.

In the water there are oxygen and carbon, the latter in dissolved form and as carbon dioxide. However, both elements exist as atoms of different weights (isotopes): oxygen, for example, as a heavy O-18 and light o-16. Isotopic water is h₂¹⁸O and has little O-16 shares. It is in the depth of the ocean because light water molecules on the surface evaporate faster and cut off to powerful ice shields during cold times; It also sinks down due to the higher salt content.

Conclusions to the octreatic circulation

In this way, the extravagances of the current octech circulation can also be examined. How the water masses flow and change their properties is far from being well known. New deep water is formed in the North Atlantic and on the Antarctic coasts. One therefore speaks of “young water”. This drives through the Atlantic and Indian Ocean, becomes warmer, which changes the chemical state and increases, enriched with nutrients. The oldest water is then in the North Pacific. The circulation time is 1000 to 1400 years.

“We have examined the flow story off the Eastern Athropist coast,” says Lembke-Jene, “and we see that there are rapid changes there. The floor water has heated up by almost a degree. As a result, the malfunction that lays the sea water melts out more from below. Because we have no long -term series of measurements, only the isotope conditions of the limestone housing of Foraminiferen could provide us with this. «

The question is: at what temperatures and when would the shelf areas completely disappear and the inland ice would slide freely into the sea? That would be the so -called tilting point. Melting the ice in turn lowers the salinity in the surface -close water and changes the entire chemism of the ocean.

Part of the carbon cycle

The future is open, but indications of the coming appear from the past. So it is advisable to get an idea of how it was once. The change of cold and warm times is still a process with many strangers. Climate models represent the changes in the near -surface water column (up to 2000 meters) quite well, but what happens in the deep ocean is unknown. We know that the world’s oceans are currently still a large part of the anthropogenic warmth and carbon dioxide. When is the level reached where the system is saturated? If more carbon gets into the ocean, the pH drops; The carbonate housings dissolve and foraminiferen die – that is the countermovement.

The small limestone shellers are part of the carbon cycle. The ratio of the stable carbon atoms C-12 and C-13, which is almost reflected in the construction of the housing, is significantly reflected. It shows how much nutrient is in the ocean, because biomass is rich in light carbon. During the cold stadiums, the transfer of ¹²C-rich biomass in the deep ocean higher than in warm stadiums.

With the transition to today’s warm period, it increases ¹³C-proportion again. However, with increasing removal of a water mass, the light carbon increases again from its origin. The warm, nutrient -rich water of today’s North Pacific is also well ventilated. “When we look back into the last warm period, the EEM interlacial, which lasted about 10,000 years and ended around 115,000, we find out because of our analyzes that the water masses of the North Pacific were more difficult to ventilate than today and during the last ice age,” says Lembke-Jene. »Surprisingly, the North Pacific seems to be in optimal condition. That surprised us. We still don’t know why this is the case. Do we live in the best possible of the worlds when it comes to the circulation of the deep water? In any case, we should do everything we can to maintain the current state. “

Look ahead into the past

The grandiose of the Foraminiferen is that their housings can be read from their housings about the age in which it was warmer than today. The rehearsals on the desk come from the middle pliocene heat period three to 3.5 million years ago. The isotope conditions showed a 2.5 degree Celsius warmer climate (always compared to the average of the pre -industrial age). We will probably have similar temperatures around the next century. The working group around Lembke-Jene tries to find out how the ocean was layered at the time and how stable the stratification was. How much carbon could he record? What did the metabolism look like with the atmosphere? This cannot be read from ice drilling nuclei, which are recorded with the deepest bore on Dom C in the Antarctic, which is completed at the end of last year.

Due to the dating of radioactive carbon components of Foraminiferen, it was demonstrated that the transition from the last cold to the warm period happened 20,000 to 11,000 years ago. Then the ocean began to ventilate better again and the values were suitable for today’s. »For the penultimate, the Holstein warm time, we recognize slightly higher temperatures than previously assumed. It was two degrees warmer than on average, and this warm time was not even very pronounced, «explains Lembke-Jene. On the other hand, the AWI specialists assume that the earliest interglacial – the time between two ice ages – lasted very long, almost over 40,000 years ago. What the little animals and their remains can tell us!

“If something is not done massively against the heating of our planet,” summarizes Lembke-Jene, “the specification of the Paris climate conference, the 1.5-degree limit of the warming, can hardly be met. Many colleagues think the trend is already irreversible. The decisions of the new black and red federal government are not very expedient. “