This week was all about lakes. From shallow to deep: Lago Juncal, Laguna Confluencia and the majestic Lago Calluqueo. Although the start of the week was a bit slower then what we had hoped for, we still managed to finish all the activities that were on our bucket list in time.
What should have been our first sampling day actually became a day of fixing the GPS for our echosounder, figuring out how to access our first lake, and finding someone who could repair an outboard engine. All it took to repair our GPS was finding the correct position for all the connections and a good amount of duct tape. The engine on the other hand was a more serious problem, one we could not handle with duct tape. We found two people, Roman Reyes and Raoul Ormeño, who were willing to take a look at it, but with little success. Roman, a 55-ish year old man with the strength of an ox, saw however that these two Belgians (these two geolocos as his wife referred to us after a funny misunderstanding) were desperately in need of a functioning engine and agreed to lend us his. He was also so kind that he invited us over for beers (which we had to bring ourselves) and a delicious dinner. Thank you, señor y señora REYes!
We have now mapped the bathymetry of Lago Juncal and Laguna Confluencia with a coverage so high it could almost be a multibeam survey. We paid special attention to the deltas where the GLOFs enter the lakes. The two rather shallow lakes display some interesting differences: L. Juncal shows a pronounced ridge in front of the delta whereas L. Confluencia has very steep slopes from the delta outward and is separated in two basins. We expected the cores (4 in L. Juncal and 2 in L. Confluencia) to contain glacial sediments – representing the proglacial flood events – intercalated in organic-rich mud – the background lake sedimentation. At first sight, through the liners, this seems to be the case, at least for Lago Confluencia… but this is for a master student to find out! Who wants to locate the GLOFs?
Our third lake, Lago Calluqueo, is a picture-perfect example of what a glacial lake looks like. This lake at the foot of Glaciar Calluqueo has been growing since the 1940’s as the glacier keeps retreating. For the GLADYS project, we are interested in how the glacier retreat is recorded in the sediments of this proglacial lake. To do this, we planned to take several cores in the lake from the glacier tongue to the river outflow. Before we even arrived, we already knew we had two difficulties to overcome. Firstly, dragging all the equipment down to the lake via a narrow, steep and slippery path was going to be a pain. Indeed with some mild back pain, sweat and the idea of science (on the way to the lake) and pisco sour (on the way up) in mind, we dragged the coring equipment, zodiac and Roman’s engine (about 200 kg of gear) to and from the lake. Secondly, knowing that the lake was over 200 m deep, coring the deepest part would be extremely difficult from a zodiac, but not impossible. “Luckily” for us, after taking some grab samples we found out that the deep basin didn’t even hold sediment (yet). We did however retrieve four cores from the distal basin, covering the entire sediment infill (about 30 cm).
Although our arms suffered and our backs hurt, we got the mud in the liners and once again a Rey saved our day (actually four days).
Next up: Tortel, to retrieve the sediment traps we deployed last year.