Temperature fluctuations inside and outside the cave

Temperature Fluctuations Inside and Outside the Cave

By Jóhannes M. Jóhannesson

The temperature inside the cave is mostly regulated by air exchange through the opening of the cave, as cold air sinks in during the wintertime and cools it down, and then during the summer time the cave heats up due to warmer temperature outside. This is a slow process and therefore the temperature inside the cave is more stable than the outside temperature. The temperature inside the cave however fluctuates during the year, from freezing temperature during the winter time, to the tropical heat of 1-4°C during the summer time. The further you go into the cave, the more stable the climate is and most of the cave does not fall below freezing during the wintertime. It depends on how cold, and how stable, the outside temperature is during the winter time on how far into the cave the temperature drops below freezing. Last winter was both cold and stable, and therefore colder temperatures reached further into the cave than we have seen before and since we are a curios bunch of people here at the Cave we decided to investigate the matter a bit more. We put up a few thermometers in the cave this summer, to study the temperature fluctuation of the cave, and we like to share the results from two of the thermostats with you (the ones with the larges fluctuations in temperature and therefore the most exciting ones). One of these thermostats is inside the cave and the second is outside the cave. The first thermostat is in a room called the cafeteria (fig. 1) and is the part of the cave that goes through the highest temperature fluctuations during the seasons. During the summertime it can be quite pleasant in the cafeteria, about 1-3° C, but during last winter the coldest temperature recorded was -11,1°C while it was usually around -6°C in there. The second thermostat is in the opening of the cave (fig. 1.) and therefore records the rise and drop of the outside temperature between day and night.



Fig. 1. Map of the cave with the entrance of the cave and the location of the cafeteria marked by blue arrows. The locations of the thermostats within the cave are marked by red. The ice extent during the winters of 2016-2017 and 2017-2018 are shown with yellow, with ice extending further into the cave last winter than the previous one.


The graph below (fig. 2.) shows the temperature measurements from those two locations from 18th of June to 7th of September. The first thing you notice (at least for people staying in this region) is how cold and miserable this summer has been, and that we have hit 0°C during the night already, so …. Winter is coming! (don’t worry, we supply everybody with dragon glass as they go on our tour)

As you can see from the graph (fig. 2.), the outside temperature is considerable higher than the temperature inside the cave and has a daily drop and rise in the temperature, showing a rise in the heat during the day and drop during the night. Inside the cave the temperature has been somewhat stable, with slow increase in temperature during the early part of the summer and then hovering between 1 and 2 °C for the last month and a half. Once the temperature inside reached 1°C there seems to be a minor correlation between the outside and inside temperature (fig 2.), where there is a slight delay in the warming up or cooling down inside the cave as the temperature changes outside.


Fig. 2. Graph showing the temperature change from 18th of June to the 7th of September 2018. The purple line shows the temperature inside the cave (cafeteria) while the blue line shows the outside temperature (the opening of the cave)


One of the coolest things about this summer has been how slowly the ice has been melting inside the cave. We still have quite a lot of ice stalagmites inside the cave, which is unusual for this time of the year since they have usually melted away by end of June or early July. This lack of melting is of course do to the cold temperature inside the cave, which is probably affected by how cold the spring and the summer have been and the large quantity of ice that was inside the cave after last winter, which might be slowing down the warming of the cave. It is therefore going to be quite interesting to see how quickly the cave will cool down this fall/winter, and if we see ice starting to form earlier than usual, we will keep you updated on that.