Past temperature in Greenland adjusted

The revised Greenland temperature history (black curve, grey uncertainties) for the period 18,000 to 10,000 before present. This temperature history is based on temperature interpretation from nitrogen measurements (green curve) and O18 diffusion measurements (red curve). The blue curve is from a previous study, based on nitrogen measurements. -  Niels Bohr Institute
The revised Greenland temperature history (black curve, grey uncertainties) for the period 18,000 to 10,000 before present. This temperature history is based on temperature interpretation from nitrogen measurements (green curve) and O18 diffusion measurements (red curve). The blue curve is from a previous study, based on nitrogen measurements. – Niels Bohr Institute

One of the common perceptions about the climate is that the amount of carbon dioxide in the atmosphere, solar radiation and temperature follow each other – the more solar radiation and the more carbon dioxide, the hotter the temperature. This correlation is also seen in the Greenland ice cores that are drilled through the approximately three kilometer thick ice sheet. But during a period of several thousand years up until the last ice age ended approximately 12,000 years ago, this pattern did not fit and this was a mystery to researchers. Now researchers from the Niels Bohr Institute have solved this mystery using new analytical techniques. The results are published in the prestigious scientific journal Science.

The Greenland ice sheet is an archive of knowledge about the Earth’s climate more than 125,000 years back in time. The ice was formed by the precipitation that fell as snow from the clouds and remained year after year, gradually being compressed into ice. By drilling down through the approximately three kilometer thick ice sheet, the researchers draw up ice cores, which provide detailed knowledge of the climate of the past annual layer after annual layer. By measuring the content of the special oxygen isotope O18 in the ice cores, you can get information about the temperature in the past climate, year by year.

But something didn’t fit. In Greenland, the end of the Ice Age started 15,000 years ago and the temperature rose quickly. Then it became colder again until 12,000 years ago, when there was again a rapid rise in temperature. The first rise in temperature is called the Bølling-Allerød interstadial and the second is called the Holocene interglacial.

Temperatures contrary to expectations

“We could see that the concentration of carbon dioxide and solar radiation was higher during the cold period between the two warm periods compared with the cold period before the first warming 15,000 years ago. But the temperature measurements based on the oxygen isotope O18 showed that the period between the two warm periods was colder than the cold period before the first warming 15,000 years ago. This was the exact opposite of what you would expect,” explains postdoc Vasileios Gkinis, Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen.

The researchers investigated ice cores from three different Greenland ice cores: the NEEM project, the NGRIP project and the GISP 2 project. But amount of the oxygen isotope O18 was not enough to reconstruct period temperatures in detail or their geographic distribution.

To get more detailed temperature data, the researchers used two relatively new methods of investigation, both of which examine the layer of compressed granular snow that is formed between the top layer of soft and fluffy snow and the layer deeper down in the ice sheet, where the compressed snow has been turned into ice. This process of transforming the fluffy snow into hard ice is physical and both the thickness and the movement of the water molecules are dependent on the temperature.

“With the first method, we measured the nitrogen content and by measuring the relationship between the two isotopes of nitrogen, N15 and N14, we could reconstruct the thickness of the compressed snow 19,000 years back in time,” explains Vasileios Gkinis.

The second method involved measuring the spread of air with water molecules with different isotope composition in the layers with the compressed snow. This process of smoothing the original water isotope variations from precipitation is dependent on the temperature, as the water molecules in vapour form are more mobile at warmer temperatures.

Temperatures ‘fall into place’

Data for the spread of the water molecules in the individual annual layers in the Greenland ice cores has thus made it possible to calculate the temperature in the layers with compressed snow 19,000 years back in time.

“What we discovered was that the previous temperature curve, which was only based on the measurements of the oxygen isotope O18, was inaccurate. The oxygen temperature curve said that the climate in central Greenland was colder around 12,000 years ago than around 15,000 years ago, despite the fact that two key climate drivers – carbon dioxide in the atmosphere and solar radiation – would suggest the opposite. With our new, more direct reconstruction, we have been able to show that the climate in central Greenland was actually warmer around 12,000 years ago compared to 15,000 years ago. So the temperatures actually follow the solar radiation and the amount of carbon dioxide in the atmosphere. We estimate that the temperature difference was 2-6 degrees,” says Bo Vinther, Associate Professor at the Centre for Ice and Climate at the Niels Bohr Institute, University of Copenhagen.

Scientists obtain new data on the weather 10,000 years ago from sediments of a lake in Sierra Nevada

University of Granada researchers are collecting samples in an Alpine lake in Sierra Nevada (Granada). -  UGRdivulga
University of Granada researchers are collecting samples in an Alpine lake in Sierra Nevada (Granada). – UGRdivulga

A research project which counts with the participation of the University of Granada has revealed new data on the climate change that took place in the Iberian Peninsula around the mid Holocene (around 6.000 years ago), when the amount of atmospheric dust coming from the Sahara increased. The data came from a study of the sediments found in an Alpine lake in Sierra Nevada (Granada)

This study, published in the journal Chemical Geology, is based on the sedimentation of atmospheric dust from the Sahara, a very frequent phenomenon in the South of the Iberian Peninsula. This phenomenon is easily identified currently, for instance, when a thin layer of red dust can be occasionally found on vehicles.

Scientists have studied an Alpine lake in Sierra Nevada, 3020 metres above sea level, called Rio Seco lake. They collected samples from sediments 1,5 metres deep, which represent approximately the last 11.000 years (a period known as Holocene), and they found, among other paleoclimate indicators, evidence of atmospheric dust coming from the Sahara. According to one of the researchers in this study, Antonio García-Alix Daroca, from the University of Granada, “the sedimentation of this atmospheric dust over the course of the Holocene has affected the vital cycles of the lakes in Sierra Nevada, since such dust contains a variety of nutrients and / or minerals which do not abound at such heights and which are required by certain organisms which dwell there.”

More atmospheric dust from the Sahara

This study has also revealed the existence of a relatively humid period during the early phase of the Holocene (10.000 – 6.000 years approximately). This period witnessed the onset of an aridification tendency which has lasted until our days, and it has coincided with an increase in the fall of atmospheric dust in the South of the Ibeian Peninsula, as a result of African dust storms.

“We have also detected certain climate cycles ultimately related to solar causes or the North Atlantic Oscillacion (NAO)”, according to García-Alix. “Since we do not have direct indicators of these climate and environmental changes, such as humidity and temperature data, in order to conduct this research we have resorted to indirect indicators, such as fossil polen, carbons and organic and inorganic geochemistry within the sediments”.

Warm US West, cold East: A 4,000-year pattern

<IMG SRC="/Images/485889256.jpg" WIDTH="350" HEIGHT="262" BORDER="0" ALT="University of Utah geochemist Gabe Bowen led a new study, published in Nature Communications, showing that the curvy jet stream pattern that brought mild weather to western North America and intense cold to the eastern states this past winter has become more dominant during the past 4,000 years than it was from 8,000 to 4,000 years ago. The study suggests global warming may aggravate the pattern, meaning such severe winter weather extremes may be worse in the future. – Lee J. Siegel, University of Utah.”>
University of Utah geochemist Gabe Bowen led a new study, published in Nature Communications, showing that the curvy jet stream pattern that brought mild weather to western North America and intense cold to the eastern states this past winter has become more dominant during the past 4,000 years than it was from 8,000 to 4,000 years ago. The study suggests global warming may aggravate the pattern, meaning such severe winter weather extremes may be worse in the future. – Lee J. Siegel, University of Utah.

Last winter’s curvy jet stream pattern brought mild temperatures to western North America and harsh cold to the East. A University of Utah-led study shows that pattern became more pronounced 4,000 years ago, and suggests it may worsen as Earth’s climate warms.

“If this trend continues, it could contribute to more extreme winter weather events in North America, as experienced this year with warm conditions in California and Alaska and intrusion of cold Arctic air across the eastern USA,” says geochemist Gabe Bowen, senior author of the study.

The study was published online April 16 by the journal Nature Communications.

“A sinuous or curvy winter jet stream means unusual warmth in the West, drought conditions in part of the West, and abnormally cold winters in the East and Southeast,” adds Bowen, an associate professor of geology and geophysics at the University of Utah. “We saw a good example of extreme wintertime climate that largely fit that pattern this past winter,” although in the typical pattern California often is wetter.

It is not new for scientists to forecast that the current warming of Earth’s climate due to carbon dioxide, methane and other “greenhouse” gases already has led to increased weather extremes and will continue to do so.

The new study shows the jet stream pattern that brings North American wintertime weather extremes is millennia old – “a longstanding and persistent pattern of climate variability,” Bowen says. Yet it also suggests global warming may enhance the pattern so there will be more frequent or more severe winter weather extremes or both.

“This is one more reason why we may have more winter extremes in North America, as well as something of a model for what those extremes may look like,” Bowen says. Human-caused climate change is reducing equator-to-pole temperature differences; the atmosphere is warming more at the poles than at the equator. Based on what happened in past millennia, that could make a curvy jet stream even more frequent and-or intense than it is now, he says.

Bowen and his co-authors analyzed previously published data on oxygen isotope ratios in lake sediment cores and cave deposits from sites in the eastern and western United States and Canada. Those isotopes were deposited in ancient rainfall and incorporated into calcium carbonate. They reveal jet stream directions during the past 8,000 years, a geological time known as middle and late stages of the Holocene Epoch.

Next, the researchers did computer modeling or simulations of jet stream patterns – both curvy and more direct west to east – to show how changes in those patterns can explain changes in the isotope ratios left by rainfall in the old lake and cave deposits.

They found that the jet stream pattern – known technically as the Pacific North American teleconnection – shifted to a generally more “positive phase” – meaning a curvy jet stream – over a 500-year period starting about 4,000 years ago. In addition to this millennial-scale change in jet stream patterns, they also noted a cycle in which increases in the sun’s intensity every 200 years make the jet stream flatter.

Bowen conducted the study with Zhongfang Liu of Tianjin Normal University in China, Kei Yoshimura of the University of Tokyo, Nikolaus Buenning of the University of Southern California, Camille Risi of the French National Center for Scientific Research, Jeffrey Welker of the University of Alaska at Anchorage, and Fasong Yuan of Cleveland State University.

The study was funded by the National Science Foundation, National Natural Science Foundation of China, Japan Society for the Promotion of Science and a joint program by the society and Japan’s Ministry of Education, Culture, Sports, Science and Technology: the Program for Risk Information on Climate Change.

Sinuous Jet Stream Brings Winter Weather Extremes

The Pacific North American teleconnection, or PNA, “is a pattern of climate variability” with positive and negative phases, Bowen says.

“In periods of positive PNA, the jet stream is very sinuous. As it comes in from Hawaii and the Pacific, it tends to rocket up past British Columbia to the Yukon and Alaska, and then it plunges down over the Canadian plains and into the eastern United States. The main effect in terms of weather is that we tend to have cold winter weather throughout most of the eastern U.S. You have a freight car of arctic air that pushes down there.”

Bowen says that when the jet stream is curvy, “the West tends to have mild, relatively warm winters, and Pacific storms tend to occur farther north. So in Northern California, the Pacific Northwest and parts of western interior, it tends to be relatively dry, but tends to be quite wet and unusually warm in northwest Canada and Alaska.”

This past winter, there were times of a strongly curving jet stream, and times when the Pacific North American teleconnection was in its negative phase, which means “the jet stream is flat, mostly west-to-east oriented,” and sometimes split, Bowen says. In years when the jet stream pattern is more flat than curvy, “we tend to have strong storms in Northern California and Oregon. That moisture makes it into the western interior. The eastern U.S. is not affected by arctic air, so it tends to have milder winter temperatures.”

The jet stream pattern – whether curvy or flat – has its greatest effects in winter and less impact on summer weather, Bowen says. The curvy pattern is enhanced by another climate phenomenon, the El Nino-Southern Oscillation, which sends a pool of warm water eastward to the eastern Pacific and affects climate worldwide.

Traces of Ancient Rains Reveal Which Way the Wind Blew

Over the millennia, oxygen in ancient rain water was incorporated into calcium carbonate deposited in cave and lake sediments. The ratio of rare, heavy oxygen-18 to the common isotope oxygen-16 in the calcium carbonate tells geochemists whether clouds that carried the rain were moving generally north or south during a given time.

Previous research determined the dates and oxygen isotope ratios for sediments in the new study, allowing Bowen and colleagues to use the ratios to tell if the jet stream was curvy or flat at various times during the past 8,000 years.

Bowen says air flowing over the Pacific picks up water from the ocean. As a curvy jet stream carries clouds north toward Alaska, the air cools and some of the water falls out as rain, with greater proportions of heavier oxygen-18 falling, thus raising the oxygen-18-to-16 ratio in rain and certain sediments in western North America. Then the jet stream curves south over the middle of the continent, and the water vapor, already depleted in oxygen-18, falls in the East as rain with lower oxygen-18-to-16 ratios.

When the jet stream is flat and moving east-to-west, oxygen-18 in rain is still elevated in the West and depleted in the East, but the difference is much less than when the jet stream is curvy.

By examining oxygen isotope ratios in lake and cave sediments in the West and East, Bowen and colleagues showed that a flatter jet stream pattern prevailed from about 8,000 to 4,000 years ago in North America, but then, over only 500 years, the pattern shifted so that curvy jet streams became more frequent or severe or both. The method can’t distinguish frequency from severity.

The new study is based mainly on isotope ratios at Buckeye Creek Cave, W. Va.; Lake Grinell, N.J.; Oregon Caves National Monument; and Lake Jellybean, Yukon.

Additional data supporting increasing curviness of the jet stream over recent millennia came from seven other sites: Crawford Lake, Ontario; Castor Lake, Wash.; Little Salt Spring, Fla.; Estancia Lake, N.M.; Crevice Lake, Mont.; and Dog and Felker lakes, British Columbia. Some sites provided oxygen isotope data; others showed changes in weather patterns based on tree ring growth or spring deposits.

Simulating the Jet Stream

As a test of what the cave and lake sediments revealed, Bowen’s team did computer simulations of climate using software that takes isotopes into account.

Simulations of climate and oxygen isotope changes in the Middle Holocene and today resemble, respectively, today’s flat and curvy jet stream patterns, supporting the switch toward increasing jet stream sinuosity 4,000 years ago.

Why did the trend start then?

“It was a when seasonality becomes weaker,” Bowen says. The Northern Hemisphere was closer to the sun during the summer 8,000 years ago than it was 4,000 years ago or is now due to a 20,000-year cycle in Earth’s orbit. He envisions a tipping point 4,000 years ago when weakening summer sunlight reduced the equator-to-pole temperature difference and, along with an intensifying El Nino climate pattern, pushed the jet stream toward greater curviness.

New study determines more accurate method to date tropical glacier moraines

The Quelccaya Ice Cap, the world's largest tropical ice sheet, is rapidly melting. -  Meredith Kelly
The Quelccaya Ice Cap, the world’s largest tropical ice sheet, is rapidly melting. – Meredith Kelly

A Dartmouth-led team has found a more accurate method to determine the ages of boulders deposited by tropical glaciers, findings that will likely influence previous research of how climate change has impacted ice masses around the equator.

The study appears in the journal Quaternary Geochronology. A PDF of the study is available on request.

Scientists use a variety of dating methods to determine the ages of glacial moraines around the world, from the poles where glaciers are at sea level to the tropics where glaciers are high in the mountains. Moraines are sedimentary deposits that mark the past extents of glaciers. Since glaciers respond sensitively to climate, especially at high latitudes and high altitudes, the timing of glacial fluctuations marked by moraines can help scientists to better understand past climatic variations and how glaciers may respond to future changes.

In the tropics, glacial scientists commonly use beryllium-10 surface exposure dating. Beryllium-10 is an isotope of beryllium produced when cosmic rays strike bedrock that is exposed to air. Predictable rates of decay tell scientists how long ago the isotope was generated and suggest that the rock was covered in ice before then. Elevation, latitude and other factors affect the rate at which beryllium-10 is produced, but researchers typically use rates taken from calibration sites scattered around the globe rather than rates locally calibrated at the sites being studied.

The Dartmouth-led team looked at beryllium-10 concentrations in moraine boulders deposited by the Quelccaya Ice Cap, the largest ice mass in the tropics. Quelccaya, which sits 18,000 feet above sea level in the Peruvian Andes, has retreated significantly in recent decades. The researchers determined a new locally calibrated production rate that is at least 11 percent to 15 percent lower than the traditional global production rate.

“The use of our locally calibrated beryllium-10 production rate will change the surface exposure ages reported in previously published studies at low latitude, high altitude sites and may alter prior paleoclimate interpretations,” said Assistant Professor Meredith Kelly, the study’s lead author and a glacial geomorphologist at Dartmouth.

The new production rate yields beryllium-10 ages that are older than previously reported, which means the boulders were exposed for longer than previously estimated. Prior studies suggested glaciers in the Peruvian Andes advanced during early Holocene time 8,000 -10,000 years ago, a period thought to have been warm but perhaps wet in the Andes. But the new production rate pushes back the beryllium-10 ages to 11,000 -12,000 years ago when the tropics were cooler and drier. Also during this time, glaciers expanded in the northern hemisphere, which indicates a relationship between the climate mechanisms that caused cooling in the northern hemisphere and southern tropics.

The findings suggest the new production rate should be used to deliver more precise ages of moraines in low-latitude, high-altitude locations, particularly in the tropical Andes. Such precision can help scientists to more accurately reconstruct past glacial and climatic variations, Kelly said.

Preparing for the next megathrust

Understanding the size and frequency of large earthquakes along the Pacific coast of North America is of great importance, not just to scientists, but also to government planners and the general public. The only way to predict the frequency and intensity of the ground motion expected from large and giant “megathrust ” earthquakes along Canada’s west coast is to analyze the geologic record. A new study published today in the Canadian Journal of Earth Sciences presents an exceptionally well-dated first record of earthquake history along the south coast of BC. Using a new high-resolution age model, a team of scientists meticulously identified and dated the disturbed sedimentary layers in a 40-metre marine sediment core raised from Effingham Inlet. The disturbances appear to have been caused by large and megathrust earthquakes that have occurred over the past 11,000 years.

One of the co-authors of the study, Dr. Audrey Dallimore, Associate Professor at Royal Roads University explains: “Some BC coastal fjords preserve annually layered organic sediments going back all the way to deglacial times. In Effingham Inlet, on the west coast of Vancouver Island, these sediments reveal disturbances we interpret were caused by earthquakes. With our very detailed age model that includes 68 radiocarbon dates and the Mazama Ash deposit (a volcanic eruption that took place 6800 yrs ago); we have identified 22 earthquake shaking events over the last 11,000 years, giving an estimate of a recurrence interval for large and megathrust earthquakes of about 500 years. However, it appears that the time between major shaking events can stretch up to about a 1,000 years.

“The last megathrust earthquake originating from the Cascadia subduction zone occurred in 1700 AD. Therefore, we are now in the risk zone of another earthquake. Even though it could be tomorrow or perhaps even centuries before it occurs, paleoseismic studies such as this one can help us understand the nature and frequency of rupture along the Cascadia Subduction Zone, and help Canadian coastal communities to improve their hazard assessments and emergency preparedness plans.”

“This exceptionally well-dated paleoseismic study by Enkin et al., involved a multi-disciplinary team of Canadian university and federal government scientists, and a core from the 2002 international drill program Marges Ouest Nord Américaines (MONA) campaign,” says Dr. Olav Lian, an associate editor of the Canadian Journal of Earth Sciences, professor at the University of the Fraser Valley and Director of the university’s Luminescence Dating Laboratory. “It gives us our first glimpse back in geologic time, of the recurrence interval of large and megathrust earthquakes impacting the vulnerable BC outer coastline. It also supports paleoseismic data found in offshore marine sediment cores along the US portion of the Cascadia Subduction Zone, recently released in an important United States Geological Survey (USGS) paleoseismic study by a team of researchers led by Dr. Chris Goldfinger of Oregon State University. In addition to analyzing the Effingham Inlet record for earthquake events, this study site has also revealed much information about climate and ocean changes throughout the Holocene to the present. These findings also clearly illustrate the importance of analyzing the geologic record to help today’s planners and policy makers, and ultimately to increase the resiliency of Canadian communities. “

Sediments from the Enol lake reveal more than 13,500 years of environmental history

This is a research campaign in the Enol lake. -  Ana Moreno et al./IPE(CSIC)
This is a research campaign in the Enol lake. – Ana Moreno et al./IPE(CSIC)

A team of Spanish researchers have used different geological samples, extracted from the Enol lake in Asturias, to show that the Holocene, a period that started 11,600 years ago, did not have a climate as stable as was believed.

The Holocene period, which includes the last 11,600 years of our history, has always been described as a stable period in terms of climatic conditions, especially when compared to the abrupt changes that occurred in the last ice age, which ended around 10,000 years ago, giving way to the Holocene.

A study carried out by researchers from the Pyrenean Institute of Ecology (IPE) at the Spanish Research Scientific Council (CSIC), in collaboration with other scientists from Zaragoza, La Coruña, Valencia and Cádiz universities, and published in the Journal of Paleolimnology, has found climatic differences amongst the “stable” 13,500 years.

The study specifically focused on the Enol lake (Asturias), where various sediment samples were extracted from the bottom. These samples provide data about the regional humidity and temperature changes in the area over more than 135 centuries.

The project, together with a previous study that details the last ice age and another, more recent one that examines the last centuries, implies “the first time glacial evolution and climate change have been registered in the last 40,000 years in the Picos de Europa National Park” claims Ana Moreno, researcher from the IPE-CSIC and lead author of the study.

The Enol lake was formed 40,000 years ago following the retreat of a glacier which dug a trough, allowing the accumulation of sediments and water. 18,000 years ago it was already a lake and organic sediments that are currently being studied were starting to be deposited.

From the lake sediments the physical properties and the amounts of organic carbon, carbonate and other elements, could be analysed, as well as some biological indicators, such as diatom and ostracod fossils.

Vegetation cover evolution

Furthermore, the detailed study of pollen accumulated in this material allows us to make a reconstruction of the variations of vegetation cover, which is crucial information in the context of climate change and the impact of human beings.

The researchers recognised at least 4 different stages in the Holocene: the first one was cold and dry, between 13,500 to 11,600 years ago (cal years BP) which included a brief return to the icy condition known as Younger Dryas. This was followed by a period of higher temperature and humidity, between 11,600 and 8,700 years ago, which coincided with the beginning of the Holocene.

The third period had a drier climate, between 8,700 and 4,650 years ago, and finally a return to the more humid climate from then up to 2,220 years ago. The study also highlights the changes caused in the latest period caused by human activity, specifically from pasture and deforestation.

The study’s conclusions therefore report significant environmental changes throughout the last 13,500 years in history. They also show how at the beginning of the Holocene, the vegetation coverage of the area, which until that time had consisted of Pinus (pine), Betula (birch) and Quercus (oak), then became a forest of mainly Quercus.

Researchers also highlight an increase in precipitation for nearly twelve centuries (between 9,750 and 8,600 years ago), which led to an increase in Corylus, or in other words, Hazel. Although the study of these geological traces from the Enol lake only covers up to 2,200 years ago, it is possible to determine the environmental impact that the region’s inhabitants of that time had from studying the pollen.

Former use of mountain pastures

Moreno said that “The use of mountain pastures is possibly the oldest documented human activity in the area. As we have seen, the lengthy sampling of Lago Enol detected that an opening in the landscape began 4,650 years ago, and most notably from 2,700 years ago”.

The results also show that from 4,650 years ago, humans contributed a greater presence of herbaceous species (from the Plantago and Rumex Acetosella genera) and a decrease in the area’s woodlands.

Those in charge of the study claim that these hydrological and landscape stages from the Enol lake sediments demonstrate the biggest changes in the climate registered during the Holocene in the south of Europe. The Cantabria mountains were like that 2,200 years ago, a date that coincided with the Roman occupation and the start of the Second Punic Wars against the Carthaginians led by Hannibal.

In a more recent study, these researchers found from the pollen register that there have been many alterations in the landscape, which were caused by human activity in the last 200 years. For example, they detected a change in the number of coprophilious fungi (which feed on the faeces of the livestock that graze there) throughout the twentieth century.

According to the researchers, this is due to the fact that “the indigenous bovine livestock were replaced by Alpine Brown cattle, and, before that, high-milk yielding Frisians. This way it changes from being an extensive livestock on the mountain, with the indigenous cattle, to another intensive type, with stables at the bottom of the valley. Another change that the pollen shows is the introduction of eucalyptus plants in 1930.

Cardiac fibrillation of the climate

In the current issue of the Scientific Journal Nature Geoscience a group of Norwegian, Swiss and German geoscientists prove that before the set-in of the Holocene very rapid climate changes already existed. The transition from the stable cold period took place about 12 150 to 11 700 years ago with very rapid fluctations up to the temperatur-threshold at which the Holocene began.

For this study, a group of scientists around J. Bakke, University of Bergen, examined sediments from Lake Kråkenes in Southwest Norway. These micro-layered lake deposits constitute a particularly suitable geological archive, with which scientists are able to analyse the climate volatility. The geochemical determination of titanium in sediments shows that during this phase significant short-term fluctuations in the titanium concentrations in the lake are detectable.

“We ascribe this to the short-term fluctuations in watermelt runoff from the inland glacier which feeds this lake”, explains Professor Gerald Haug from the DFG Leibniz Center for Earth Surface Process and Climate Studies at the University of Potsdam and the ETH Zürich, who carried out the analysis together with his colleague, Peter Dulkski, from the GFZ German Research Centre for Geosciences. “The fluctuating glacialmelt is a result of the intermittent advancement of the Gulf Stream and the resulting successive retreat of the sea-ice coverage.”

This process is closely linked with an equally high-frequence change in the westwind system and the therewith connected heat transport to Europe. This cardiac fibrillation of the climate is reflected again, as shown, in the fast-varying meltwater runoff into the examined lake, which at this point in time actually lay at the most climate-sensitive location of Europe, namely there where the Gulf Stream and the sea-ice coverage transformed.