DOI: 10.5061/dryad.s1rn8pkjj
title: Data from: Differential cooling of a freshwater body below the temperature of maximum density

description: We propose a simplified model for the time rate of change of average basin
 temperature for a freshwater lake which has two connected basins: a
 shallow littoral zone of depth D1, and a deeper main basin of depth D2.
 This system is cooled below the temperature of maximum density (Tmd) with
 a constant and uniform outgoing surface heat flux, Ho. The differential
 cooling that is established via this setup gives rise to an exchange flow
 between the two basins, which we approximate as a time-dependent heat flux
 controlled by the strength of the time-dependent density difference
 between the two basins. Our model is a coupled system of two
 ordinary differential equations, which allows for a process-based
 investigation into the importance of exchange on the timing of ice-onset
 for a lake with a shallow littoral zone. While basin geometry plays a role
 in the overall timing of ice-onset for the system, it is the relative
 strength of Ho to the exchange flow-related heat flux due to the
 density anomaly of fresh water, ρ*, which dictates the behaviour of the
 cooling system. We show that at sufficiently large values of the heat flux
 ratio, Φ, the difference in timing of ice onset between the littoral zone
 and main basin becomes insensitive to the initial conditions in the lake.
 We use data from Base Mine Lake, Canada, to both verify our model
 assumptions and evaluate the predictions made by our simple model.
description: Temperature data used in this study and included in this dataset
 were collected using RBR SoloT temperature loggers (0.002 °C accuracy)
 located at the Southwest platform (P3) mooring at Base Mine Lake (57°
 1' N, 111° 37' W in Alberta, Canada). We have excluded the
 temperature measurements made at 9 m depth from the dataset here, as these
 measurements were made in the mud at the bottom of the lake, and thus not
 used in the present study. Hourly average wind speeds shown in the
 corresponding manuscript were measured at 3.3 m above the lake surface at
 the central platform (P1) at Base Mine Lake. For further information on
 data collection and processing, please refer to Tedford et al
 (2019). The Excel spreadsheet of lake coverage
 observations was generated by Karin Huang in 2017. The observations for
 'Status' in this spreadsheet were analysed to identify ice onset
 times used in the corresponding manuscript. Images corresponding with the
 before and after times of observed ice-onset in both the littoral zone and
 main basin are included as validation of the observations made and
 recorded by Karin.  Tedford, T., Halferdahl, G.,
 Pieters, R., and Lawrence, G. A. (2019): Temporal variations in turbidity
 in an oil sands pit lake. <em>Environmental Fluid
 Mechanics</em> <strong>19</strong>: 457-473. https://doi.org/10.1007/s10652-018-9632-6
description: # Data from: Differential cooling of a freshwater body below the
 temperature of maximum density
 [https://doi.org/10.5061/dryad.s1rn8pkjj](https://doi.org/10.5061/dryad.s1rn8pkjj) ## Description of the data and file structure This data was used to identify when both the littoral zone and main basin of Base Mine Lake experienced surface ice onset in the fall of 2015. The temperature data were used to define a seasonal cooling rate to use in a simple box model derived to predict ice onset in a lake that experiences differential cooling. This dataset includes three files: "BML_P3_Temperature_data.csv", "BML_P1_Wind_data.csv", and "November_2015_Base_Mine_Lake_Observations.xlsx". All missing data represented as NA. ### Files and variables #### BML_P3_Temperature_data.csv Temperature data taken at 9 depths (0.5 m, 1 m, 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, and 9 m) at a frequency of 0.1 Hz (every 10 seconds) between DOY 275 (2 October 2015, at 00:00 LT) and DOY 330 (26 November 2015, at 23:59:50 LT). There are no headings in the CSV file, and the structure should be (# of variables, observations). Variables are organised as follows: * DOY in 2015: In local time (Alberta, Canada) * Temperature at 0.5 m depth (degrees Celsius) * Temperature at 1.0 m depth (degrees Celsius) * Temperature at 2.0 m depth (degrees Celsius) * Temperature at 3.0 m depth (degrees Celsius) * Temperature at 4.0 m depth (degrees Celsius) * Temperature at 5.0 m depth (degrees Celsius) * Temperature at 6.0 m depth (degrees Celsius) * Temperature at 7.0 m depth (degrees Celsius) * Temperature at 8.0 m depth (degrees Celsius) #### BML_P1_Wind_data.csv Hourly average wind speed data taken at 3.3 m height above the lake water level between DOY 275 (2 October 2015, at 00:00 LT) and DOY 330 (26 November 2015, at 23:00:00 LT). There are no headings in the CSV file, and the structure should be (# of variables, observations). Variables are organised as follows: * DOY in 2015: In local time (Alberta, Canada) * Average hourly wind speed (meters per second) #### November_2015_Base_Mine_Lake_Observations.xlsx Excel spreadsheet with 5 tabs for each camera pointed towards the surface of Base Mine Lake. Camera 2 faces the littoral zone, cameras 1, 3, 4, and 5 face the main basin. Observations were made by Karin Huang based on phenocamera images taken and logged every hour between 10:00 LT and 15:00 LT. The purpose of this original dataset was for observations of oil contamination on the surface of the lake. For clarity, we have only included the observations that are relevant for the determination of whether there was ice on the lake surface or not. Missing text data is denoted by "null", and missing numeric data is denoted by "NA". When comment information is missing, either the comment was related to oil sheen on the lake surface, surface wave activity, or there were no additional comments made by Karin Huang. When "Status" or "% Ice" data is missing, the reason is due to snow covering the camera lens (as noted in the comments). The variables in the dataset are as follows: * Date * Time (LT) * DateTime: Date Time (LT) * Image: ID number for image * Status: Observation of the lake surface * % Ice: Percentage of ice coverage observed in the image * Comment: Unknown what some of the comments refer to #### Images included * IMG_0295.JPG: Image of main basin surface at 15:00 LT 18 November 2015 (from Camera 5) * IMG_0296.JPG  Image of main basin surface at 10:00 LT 19 November 2015 (from Camera 5; presumed Ice onset time for main basin) * IMG_2629.JPG :Image of littoral zone surface at 14:00 LT 15 November 2015 (from Camera 2) * IMG_2630.JPG : mage of littoral zone surface at 15:00 LT 15 November 2015 (from Camera 2; presumed Ice onset time for littoral zone) Note: To know more about the data and for the images, please contact the Corresponding author: Kelsey Everard ([kae10022@nyu.edu](mailto:kae10022@nyu.edu)) ## Access information Other publicly accessible locations of the data: * None Data was derived from the following sources: * None