Researchers led by Yuko Motizuki of the Astro-Glaciology Laboratory at the RIKEN Nishina Center in Japan have developed a new laser sampling system to study the composition of ice cores taken from glaciers. The new system has a depth resolution of 3 mm (about three times less than currently available), meaning it can detect temperature fluctuations that occurred over much shorter periods of time in the past.
The new laser sampler, or LMS, is expected to help reconstruct continuous annual temperature changes that occurred thousands to hundreds of thousands of years ago and help scientists understand past and current climate change. The study was published on: Journal of Glaciology September 19.
Tree rings can tell us how old a tree is, and the color and width of the rings can tell us a little about the local climate in those years. Annual glacier growth can tell us a similar story, but over a much longer period of time. Scientists study past climate changes by analyzing cylindrical ice cores extracted from glaciers.
By taking samples at regular intervals throughout the cores, researchers can reconstruct continuous temperature profiles. However, this is not possible in samples taken from deep regions where annual accumulation is generally compressed below one centimeter.
There are currently two standard methods of sampling ice. The depth accuracy of one is about 1cm; This means that data for years with less than 1 cm of accumulation will be lost and one-off events that significantly change the climate will be missed. Another method has high depth accuracy but destroys some of the sample needed to analyze water content, the main way scientists calculate historical temperatures.
The new laser melt sampler overcomes both of these problems; It has high depth accuracy and does not destroy critical oxygen and hydrogen isotopes in water that are needed to determine past temperature.
The LMS system passes a laser beam through a special silver-tipped optical fiber and quickly pumps out the liquid sample, eventually placing it in stainless steel vials. Once the specialized equipment was assembled, the researchers conducted experiments to optimize three critical parts of the process: the amount of power of the laser, the speed at which the nozzle should be inserted into the core as the laser melts the ice, and the speed at which the liquid sample is discharged.
The optimization allowed the researchers to melt the ice as quickly as possible, preventing the laser from overheating and the melt water from overheating; This would disrupt the balance of critical isotopes and prevent accurate temperature measurements.
To prove the concept, the team sampled a 15 cm section of a 50 cm shallow Dome-Fuji ice core taken approximately one football field (~92 m) below the ice surface in East Antarctica. In one test, they were able to take 51 individual samples at regular 3mm intervals along a section of the ice core. They measured the stable oxygen and hydrogen isotopes that make up the meltwater obtained from the samples and found that they matched well with the isotopes retrieved by manual fractionation, a process that was only practical in this research setting. A good match means that the laser melting process will not disrupt the sample and the expected temperatures will be correct.
Motizuki says: “With our laser melting method, it is now possible to analyze stable isotopes of water with a resolution of a few millimeters. This will allow researchers to obtain continuous, long-term, annual temperature profiles even in deep ice cores. “It is collected in places where accumulation is low in Antarctica, and temporary events such as sudden temperature changes are also recorded there.”
Next, the researchers plan to use the LMS system or its next updated version to study climate change associated with natural fluctuations in solar activity. Source
Source: Port Altele
