Hard thermal turbulence in Antarctic Subglacial Lakes

2020 ◽  
Author(s):  
Martin Siegert ◽  
Louis-Alexandre Couston
Keyword(s):  
Water Depth ◽  
Temperature Fluctuations ◽  
Ice Cover ◽  
Stable Layer ◽  
Convective Turbulence ◽  
Physical Conditions ◽  
Thermal Turbulence ◽  
Melt Water ◽  
Subglacial Lakes ◽  
Geothermal Flux

<p>Over 250 stable and isolated subglacial lakes exist at and close to the ice-sheet center in Antarctica. The physical conditions within subglacial lakes, and the differences between distinct lake settings, are critical to evaluating how and where life may best exist. Here, we demonstrate that upward heating by Earth’s geothermal flux provides efficient stirring of Antarctic subglacial lakes’ water, in a variety of ways related to their water depth, ice overburden and ceiling slope. We show that most lakes are in a regime of hard convective turbulence, enabling efficient mixing of nutrient- and oxygen-enriched top melt-water, which is essential for biome formation. Lakes beneath a thin (about less than 3 km) ice cover and lakes with a thick (more than 3 km) ice cover experience similarly-large velocities, but the latter have significantly larger temperature fluctuations and have a stable layer up to several tens of meters thick adjacent to the ice. We discuss the implications of hydrological conditions on the concentration of particulates in the water column.</p>

scholarly journals Dynamic flows create potentially habitable conditions in Antarctic subglacial lakes

2021 ◽  
Vol 7 (8) ◽  
pp. eabc3972
Author(s):  
Louis-Alexandre Couston ◽  
Martin Siegert
Keyword(s):  
Bulk Water ◽  
Water Sampling ◽  
Stable Layer ◽  
Microbial Life ◽  
Subglacial Lake ◽  
Physical Conditions ◽  
Dynamic Flows ◽  
Subglacial Lakes ◽  
Ice Water ◽  
The Antarctic

Trapped beneath the Antarctic ice sheet lie over 400 subglacial lakes, which are considered to be extreme, isolated, yet viable habitats for microbial life. The physical conditions within subglacial lakes are critical to evaluating how and where life may best exist. Here, we propose that Earth’s geothermal flux provides efficient stirring of Antarctic subglacial lake water. We demonstrate that most lakes are in a regime of vigorous turbulent vertical convection, enabling suspension of spherical particulates with diameters up to 36 micrometers. Thus, dynamic conditions support efficient mixing of nutrient- and oxygen-enriched meltwater derived from the overlying ice, which is essential for biome support within the water column. We caution that accreted ice analysis cannot always be used as a proxy for water sampling of lakes beneath a thin (<3.166 kilometers) ice cover, because a stable layer isolates the well-mixed bulk water from the ice-water interface where freezing may occur.

Development and validation of numerical habitat models for juveniles of Atlantic salmon (Salmo salar)

2000 ◽  
Vol 57 (10) ◽  
pp. 2065-2075 ◽  
Author(s):  
J C Guay ◽  
D Boisclair ◽  
D Rioux ◽  
M Leclerc ◽  
M Lapointe ◽  
...  
Keyword(s):  
Logistic Regression ◽  
Atlantic Salmon ◽  
Salmo Salar ◽  
Water Depth ◽  
Current Speed ◽  
Fish Distribution ◽  
Biological Model ◽  
Habitat Models ◽  
Physical Conditions ◽  
Atlantic Salmon Salmo Salar

We evaluated the ability of numerical habitat models (NHM) to predict the distribution of juveniles of Atlantic salmon (Salmo salar) in a river. NHMs comprise a hydrodynamic model (to predict water depth and current speed for any given flow) and a biological model (to predict habitat quality for fish using water depth, current speed, and substrate composition). We implemented NHMs with a biological model based on (i) preference curves defined by the ratio of the use to the availability of physical conditions and (ii) a multivariate logistic regression that distinguished between the physical conditions used and avoided by fish. Preference curves provided a habitat suitability index (HSI) ranging from 0 to 1, and the logistic regression produced a habitat probabilistic index (HPI) representing the probability of observing a parr under given physical conditions. Pearson's correlation coefficients between HSI and local densities of parr ranged from 0.39 to 0.63 depending on flow. Corresponding values for HPI ranged from 0.81 to 0.98. We concluded that HPI may be a more powerful biological model than HSI for predicting local variations in fish density, forecasting fish distribution patterns, and performing summer habitat modelling for Atlantic salmon juveniles.

scholarly journals Effects of Water Depth and Ice Thickness on Ice Cover Blasting for Ice Jam Flood Prevention: A Case Study on the Heilong River, China

Water ◽  
2018 ◽  
Vol 10 (6) ◽  
pp. 700
Author(s):  
Tao Wang ◽  
Xinlei Guo ◽  
Hui Fu ◽  
Yongxin Guo ◽  
Xuming Peng ◽  
...  
Keyword(s):  
Water Depth ◽  
Ice Cover ◽  
Ice Thickness ◽  
Flood Prevention ◽  
Ice Jam

Temperature and site selection by Blanding’s Turtles (Emydoidea blandingii) during hibernation near the species’ northern range limit

2009 ◽  
Vol 87 (9) ◽  
pp. 825-834 ◽  
Author(s):  
C. B. Edge ◽  
B. D. Steinberg ◽  
R. J. Brooks ◽  
J. D. Litzgus
Keyword(s):  
Dissolved Oxygen ◽  
Water Depth ◽  
Respiratory Acidosis ◽  
Ice Cover ◽  
Range Limit ◽  
Emydoidea Blandingii ◽  
Northern Range Limit ◽  
Overwintering Survival ◽  
Prolonged Dormancy ◽  
Selection Of

Many animals that live in northern climates enter a state of prolonged dormancy during winter. These animals possess a suite of physiological and behavioural adaptations that minimize threats to survival while overwintering. There are three major threats to overwintering survival: metabolic and respiratory acidosis, freezing, and predation. Selection of hibernation sites should minimize these threats. We monitored dissolved oxygen, water depth, and temperature at overwintering locations of Blanding’s Turtles ( Emydoidea blandingii (Holbrook, 1838)) and at stations located haphazardly in six different habitat types over two winters in Algonquin Park, Ontario, Canada. Water depth and dissolved oxygen in overwintering sites used by turtles were similar to those measured at haphazard stations. In contrast, estimated turtle body temperatures (~0 °C) were significantly lower and less variable than water temperatures measured at haphazard stations. These data and those reported elsewhere suggest that there are two alternatives for selection of suitable hibernacula by anoxia tolerant turtles. In areas where there is periodic access to aerial oxygen, turtles select sites where ice cover may not be present for the entire winter, but in areas where ice cover restricts access to air, turtles select sites where water temperatures are close to 0 °C.

scholarly journals The causes of atmospheric inhomogeneities

1963 ◽  
Vol 19 ◽  
pp. 132-143 ◽  
Author(s):  
R. S. Scorer
Keyword(s):  
Thermal Convection ◽  
Pressure Fluctuations ◽  
Temperature Fluctuations ◽  
Stable Layer ◽  
Free Air

There are several different atmospheric causes, of imperfections in the images seen in a telescope. The most serious are due to thermal convection from the ground, or the stirring of a stable layer at the ground by wind : choice of site and observatory design can reduce these effects. In the free air well away from the ground some of the largest inhomogeneities may be due essentially to large gradients of humidity, and certain cloud types indicate the mechanisms by which such inhomogeneities are established. Temperature fluctuations caused by pressure fluctuations in eddies close to the telescope are probably not serious, and can be avoided by observatory design.

EFFECTS OF WATER DEPTH AND ICE THICKNESS ON ICE COVER BLASTING FOR ICE JAM FLOOD PREVENTION

2019 ◽  
Author(s):  
GUO XINLEI ◽  
WANG TAO ◽  
FU HUI ◽  
GUO YONGXIN ◽  
LI JIAZHEN ◽  
...  
Keyword(s):  
Water Depth ◽  
Ice Cover ◽  
Ice Thickness ◽  
Flood Prevention ◽  
Ice Jam
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