Lake measurements at Ulansuhai Nur, Inner-Mongolia

I hoist the probe out of the water, put it in its case and sling the case over my shoulder. I’m surrounded by reeds, which cover a huge part of the lake. Sharp ”clings” can be heard coming from them, and as I turn my head I see a flock of bearded tits (panurus biarmicus) fly out of the reeds to the next patch looking for food. In air, I can smell smoke originating from burning biomass. The smoke is sometimes so thick that the nearby mountains, that would otherwise be dominating the landscape, are just silhouettes.

I am at Ulansuhai Nur, a large salt lake in western Inner-Mongolia. With me here are Jussi Huotari and Lauri Arvola from the University of Helsinki Lammi biological station. Through them, our university has been collaborating with Hohhot Agricultural university and Dalian University of Technology for years already, quantifying the nutrients, primary production and gas fluxes out of and into the lake. I’m representing Helsinki Uni as well, but as a INARian . I’m here for the first time, and my job is to look more into the physics of the lake via temperature, salinity and density profiles to figure out how the lake is circulating under the spring sun.

There are a few peculiar properties about the lake. First, it is very shallow. Mean depth is at around one-and-a-half meters, and maximum depth is a bit under three meters. So yes, there is a place in the lake where a fully grown adult man is able to drown. Second, the lake is quite salty, about half of that in the Gulf of Finland. And it shows in the surroundings of the lake, as the ground is sometimes white from something that at a first glance looks like snow, but is actually salt. Enough of it is accumulated to the ground that it is worth the effort to collect it by some farmers of the area. Also, since the lake is so shallow, and the ice covering is so clear, sunlight can penetrate the whole water body all the way to the sediment. And sunlight there is plenty, although in the mornings the Sun has a hard time penetrating all the smog. During the day, the Sun gets high up in the sky already in March, due to low latitude of the lake (40° N). In the middle of the day, I could hear the quiet sizzling of the ice cover as it is melting.

The station we stay at (”Observation and study of Inner Mongolia Wuliang Suhai wetland ecosystem station location country”, according to a placard decorating the front door) sits almost completely alone in the arid landscape. One other, rather modern looking building is sitting next to it, some atmospheric/meteorological research station, with no one in there. An old anti-aircraft gun sits in the front yard. Maybe they took the threat from the air a bit too literally?

Anyways, when I’m looking around I see plenty of things to study. During the day, one can smell smoke and in the night, when you turn on your headlamp, you can see light scattering from small particles in the air. The water can support massive amounts of primary production under ice, due to high nutrient concentrations and intense sunlight. The reeds provide a home to hundreds of species of birds. And the lake seems to have a very strange salinity stratification. There is ready infrastructure for research built here, so this lake and its surroundings are just waiting for other curious minds to come there!

Text by: Research assistant Joonatan Ala-Könni, Institute for Atmospheric and Earth System Research INAR, University of Helsinki

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