<p>You put the sample in a cryogenic UHV chamber or at least cryogenic sample holder (e.g. -200°C, <span class="math-container">$&lt;10^{-6}$</span>mbar) with a mass spectrometer attached to the chamber. Then you slowly melt or rather evaporate the ice (e.g. by illumination or a heater) and do a live analysis of the evaporating gases.</p>
<p>Of course you are not interested in the water itself, but anything not water will be constituents of the trapped gases inside the ice. A mass spectrometer allows to measure the relative concentrations of the detected species. For extremely low concentrations you might want to improve sensitivity by applying a chopper to your measurements to have the ability to subtract the background.</p>

CC BY-SA 4.0
2024-10-22T11:58:07.367Z
2024-10-22T12:25:24.277Z
2024-10-22T12:25:24.277Z
planetmaker
<p>I read an article about how the CO<span class="math-container">$_2$</span> concentration changed in the least 500k years, based on the analysis of air bubbles trapped in Arctic ice.</p>
<p>I came to wonder how the bubbles were extracted for further analysis. It must be a way that ensures that the surrounding air does not interfere.</p>
<p>Since it has been about 30 years I had a course on measurement (which, to be frank, I slept through) I vaguely imagine that it must be a combination of deep freezing (to slow down melting and liquify gases) and pumping the surrounding air -- something along the lines of</p>
<ul>
<li>put the sample in a closed recipient</li>
<li>deep freeze it to possibly liquefy some gazes (to be discarded)</li>
<li>pump out the air to get &quot;vacuum&quot; (where &quot;vacuum&quot; is defined according to the requested uncertainty in the measurement)</li>
<li>raise the temperature to melt the external layer - to account for gas that adheres, st the same time pumping out the air (the deep freeze should ensure that something is left of the sample)</li>
</ul>
<p>I am genuinely curious how you actually extract these bubbles with a good chance of not introducing surrounding CO<span class="math-container">$_2$</span>.</p>

<measurements><glaciology><co2><ice><air>
How to extract air bubbles from arctic ice to measure CO2 concentration?
WoJ
# How to extract air bubbles from arctic ice to measure CO2 concentration?

(Asked by: username_0 on 2024-10-22)

I read an article about how the CO$\_2$ concentration changed in the least 500k years, based on the analysis of air bubbles trapped in Arctic ice.

I came to wonder how the bubbles were extracted for further analysis. It must be a way that ensures that the surrounding air does not interfere.

Since it has been about 30 years I had a course on measurement (which, to be frank, I slept through) I vaguely imagine that it must be a combination of deep freezing (to slow down melting and liquify gases) and pumping the surrounding air -- something along the lines of

* put the sample in a closed recipient
* deep freeze it to possibly liquefy some gazes (to be discarded)
* pump out the air to get "vacuum" (where "vacuum" is defined according to the requested uncertainty in the measurement)
* raise the temperature to melt the external layer - to account for gas that adheres, st the same time pumping out the air (the deep freeze should ensure that something is left of the sample)

I am genuinely curious how you actually extract these bubbles with a good chance of not introducing surrounding CO$\_2$.

**Tags:** measurements, glaciology, co2, ice, air


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## 1 answers

### Answer by username_1 on 2024-10-22. Score: 8 | Accepted answer

You put the sample in a cryogenic UHV chamber or at least cryogenic sample holder (e.g. -200°C, $<10^{-6}$mbar) with a mass spectrometer attached to the chamber. Then you slowly melt or rather evaporate the ice (e.g. by illumination or a heater) and do a live analysis of the evaporating gases.

Of course you are not interested in the water itself, but anything not water will be constituents of the trapped gases inside the ice. A mass spectrometer allows to measure the relative concentrations of the detected species. For extremely low concentrations you might want to improve sensitivity by applying a chopper to your measurements to have the ability to subtract the background.


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