Welcome to the Greenland temperature information center

Greenland is covered by a large ice-sheet, which holds water to raise global sea-level by 7m. It has been shown that temperature is an important factor controlling the size of the Ice-sheet. Therefore, we have been investigating how Greenland varied over time especially beyond observations. This page is created by Dr. Takuro Kobashi at University of Bern, and the project is supported by EU Marie Curie Fellowship. 

Project Completed (2017/5/3)!
The final paper has been published. This completes the Greenland temperature project. 

Kobashi, T., L. Menviel, A. Jeltsch-Thömmes, B. M. Vinther, J. E. Box, R. Muscheler, T. Nakaegawa, P. L. Pfister, M. Döring, M. Leuenberger, H. Wanner, A. Ohmura, Volcanic influence on centennial to millennial Holocene Greenland temperature change, Scientific Reports, 7, Article number: 1441, 2017. pdf

Project at a Glance

We have been reconstructing Greenland temperature using ice cores, and investigate the mechanisms of the changes. Contrasting to the conventional method of using oxygen isotope of ice, we use argon and nitrogen isotopes in trapped air in ice cores. 
  • Develop a robust method of reconstruct multi-decadal temperature change in Greenland. 
  • Investigate the causes of the temperature changes.

Project Objectives

The objectives of this project is to better understand climate system in multi-decadal to longer time scale, which has substantial impacts on societal development in the past, present, and future.  
  • Understand causes of climate change in multidecadal scales or longer. 
  • Greenland temperature is highly related with ocean and atmospheric changes in the region.
  • Interpret human induced climate change within natural variability.
  • Consider human's roles in the future development of nature in a longer time scale.  

How can temperature change can be recovered from gas occluded in air? 

  • We use nitrogen and argon isotopes in air trapped in ice cores. These isotopes are constant in atmosphere for tens of thousands of years. So, any deviations in ice cores from atmospheric composition can be traced into the process in the snow (firn) layer. 
  • Gasses in the firn layer fractionate according to the depth of the layer and the temperature gradient. As the temperature sensitivity of nitrogen and argon isotopes are different, we can reconstruct temperature gradients in the firn layer by measuring nitrogen and argon isotopic ratio in bubbles within ice cores.
  • The temperature gradients estimated from ice cores can be used to reconstruct surface temperature variations by integrating the temperature gradients using firn densification and heat diffusion models.
  • We tested this method by various ways, and we found that the method can capture the surface temperature variability within estimated uncertainties. 
  • This is better than the methods which use firn densification heat diffusion model to constrain firn depths for the temperature calculations. This is largely due to the fact that firn-densification heat diffusion models are not precise enough to constrain firn thickness when the temperature variation is small like the Holocene.    

Recent findings

  • We published a paper about solar influences on Greenland temperature. The intriguing results show that multidecadal Greenland temperatures were heavy influenced by changes in Northern Hemisphere and solar activity. It is no surprise that Greenland temperature changes with North Hemisphere temperature as it is part of it, but data clearly show Greenland temperature is negatively controlled by solar activity. 
  • Greenland temperature warms when solar activity decreases, and it cools when solar activity increases (relative to Norther Hemispheric temperature trend)!  

Any questions? Send an e-mail to me (takuro.kobashi@gmail.com).