TY - JOUR
T1 - Classifying Mixing Regimes in Ponds and Shallow Lakes
AU - Holgerson, Meredith A.
AU - Richardson, David C.
AU - Roith, Joseph
AU - Bortolotti, Lauren E.
AU - Finlay, Kerri
AU - Hornbach, Daniel J.
AU - Gurung, Kshitij
AU - Ness, Andrew
AU - Andersen, Mikkel R.
AU - Bansal, Sheel
AU - Finlay, Jacques C.
AU - Cianci-Gaskill, Jacob A.
AU - Hahn, Shannon
AU - Janke, Benjamin D.
AU - McDonald, Cory
AU - Mesman, Jorrit P.
AU - North, Rebecca L.
AU - Roberts, Cassandra O.
AU - Sweetman, Jon N.
AU - Webb, Jackie R.
N1 - Publisher Copyright:
© 2022 The Authors.
PY - 2022/7
Y1 - 2022/7
N2 - Lakes are classified by thermal mixing regimes, with shallow waterbodies historically categorized as continuously mixing systems. Yet, recent studies demonstrate extended summertime stratification in ponds, underscoring the need to reassess thermal classifications for shallow waterbodies. In this study, we examined the summertime thermal dynamics of 34 ponds and shallow lakes across temperate North America and Europe to categorize and identify the drivers of different mixing regimes. We identified three mixing regimes: rarely (n = 18), intermittently (n = 10), and often (n = 6) mixed, where waterbodies mixed an average of 2%, 26%, and 75% of the study period, respectively. Waterbodies in the often mixed category were larger (≥4.17 ha) and stratification weakened with increased wind shear stress, characteristic of “shallow lakes.” In contrast, smaller waterbodies, or “ponds,” mixed less frequently, and stratification strengthened with increased shortwave radiation. Shallow ponds (<0.74 m) mixed intermittently, with daytime stratification often breaking down overnight due to convective cooling. Ponds ≥0.74 m deep were rarely or never mixed, likely due to limited wind energy relative to the larger density gradients associated with slightly deeper water columns. Precipitation events weakened stratification, even causing short-term mixing (hours to days) in some sites. By examining a broad set of shallow waterbodies, we show that mixing regimes are highly sensitive to very small differences in size and depth, with potential implications for ecological and biogeochemical processes. Ultimately, we propose a new framework to characterize the variable mixing regimes of ponds and shallow lakes.
AB - Lakes are classified by thermal mixing regimes, with shallow waterbodies historically categorized as continuously mixing systems. Yet, recent studies demonstrate extended summertime stratification in ponds, underscoring the need to reassess thermal classifications for shallow waterbodies. In this study, we examined the summertime thermal dynamics of 34 ponds and shallow lakes across temperate North America and Europe to categorize and identify the drivers of different mixing regimes. We identified three mixing regimes: rarely (n = 18), intermittently (n = 10), and often (n = 6) mixed, where waterbodies mixed an average of 2%, 26%, and 75% of the study period, respectively. Waterbodies in the often mixed category were larger (≥4.17 ha) and stratification weakened with increased wind shear stress, characteristic of “shallow lakes.” In contrast, smaller waterbodies, or “ponds,” mixed less frequently, and stratification strengthened with increased shortwave radiation. Shallow ponds (<0.74 m) mixed intermittently, with daytime stratification often breaking down overnight due to convective cooling. Ponds ≥0.74 m deep were rarely or never mixed, likely due to limited wind energy relative to the larger density gradients associated with slightly deeper water columns. Precipitation events weakened stratification, even causing short-term mixing (hours to days) in some sites. By examining a broad set of shallow waterbodies, we show that mixing regimes are highly sensitive to very small differences in size and depth, with potential implications for ecological and biogeochemical processes. Ultimately, we propose a new framework to characterize the variable mixing regimes of ponds and shallow lakes.
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U2 - 10.1029/2022WR032522
DO - 10.1029/2022WR032522
M3 - Article
AN - SCOPUS:85134880832
SN - 0043-1397
VL - 58
JO - Water Resources Research
JF - Water Resources Research
IS - 7
M1 - e2022WR032522
ER -