DOI: 10.5061/dryad.q83bk3jpc
title: Lake effect on summer cooling of shorelines and adjacent inland forests on Lake Superior’s north shore

description: Climate refugia, or areas that are projected to remain relatively stable
 under climate change, can serve as remnant habitat or steeping stones for
 species dispersal. The largest freshwater lake in the world by surface
 area, Lake Superior, serves as a model system for understanding
 cooling-mediated local refugia, as its cool summer water temperatures and
 wave action have maintained shoreline habitats suitable for disjunct
 opulations for arctic-alpine plants since deglaciation. It is known to
 affect local climates by providing a summer cooling effect near its
 shorelines, however, the inland gradient of change and spatial patterns of
 cooling has not been quantified. Here, we describe the extent of the
 inland cooling gradient, the degree of temperature buffering, and patterns
 of cooling for Lake Superior's north shore over a 3-year period.
 Specifically, we established 7 transects along Lake Superior's north
 shore, with temperature data loggers placed at 10 m, 100 m, 1 km, 10 km,
 and 100 km inland. We analyzed temperature data by year, month, summer
 maximum, and growing degree days (GDD0) for each site. Summertime cooling
 at shore sites (10m) was ~5 °C cooler than inland control sites (100 km),
 while sites 10 km from the shore were still 1.6 °C cooler than control
 sites. Magnitude of cooling varied geographically, with sites further west
 and southeast showing little to no cooling effect. Site on the exposed
 north and northeast shore where disjunct arctic-alpine plants are most
 common showed the highest degree of temperature buffering. We also found
 that shoreline sites on the north and northeast shore had shorter growing
 seasons compared to inland control sites. Finally, the number of days per
 year warmer than 16 °C, a maximum temperature threshold associated with
 arctic-alpine plant occurrences, averaged 65 days per year at 10 m sites
 and 82 days per year at control sites. The north shore of Lake Superior
 serves as a transition zone between temperate deciduous forests and boreal
 forests and is predicted to transition to deciduous forests under climate
 change. An understanding of the extent of lake-mediated cooling on
 adjacent forests can better inform risk to arctic-alpine disjunct species,
 inland forests, and overall vegetation transition models on Lake
 Superior's north shore.
description: GENERAL INFORMATION 1. Dataset title: Lake effect on summer cooling of
 shorelines and adjacent inland forests on Lake Superior’s north shore 2.
 Author Information A. Corresponding Author Contact Information Name:
 Ashley Hillman Institution: University of Alberta Email:
 B. Principal Investigator Contact Information
 Name: Scott Nielsen Institution: University of Alberta Email:
 3. Date of data collection (single date, range,
 approximate date): July 2018- July 2021 4. Geographic location of data
 collection: Lake Superior, Ontario, Canada 5. Information about funding
 sources that supported the collection of the data: Natural Sciences and
 Engineering Research Council of Canada (NSERC) DATA & FILE OVERVIEW
 This dataset contains time series temperature data for 7 transects
 arranged west to east on Lake Superior's north shore. Due to file
 size, raw data is separated by Location. Mean daily temperature is
 provideded for all data in the file Hillman_mean daily temperature.csv
 Additional files used in analysis are included, such as Growing Degree
 Days (calculated outside of R), and disjunct arctic-alpine plant
 occurrence information for each shoreline site. 1. File List: A)
 Hillman_Marathon raw data.csv B) Hillman_Montreal River Harbour raw
 data.csv C) Hillman_Rossport raw data.csv D) HIllman_Schreiber raw
 data.csv E) Hillman_Terrace Bay raw data.csv F) Hillman_Thunder Bay raw
 data.csv G) Hillman_Wawa raw data.csv H) Hillman_disjunct_prop.csv I)
 Hillman_GDD_all.csv J) Hillman\_ met station differences.csv K)
 Hillman_site differences.csv
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: All raw data files 1. Variable List: * Year
 - Year of data collection * Month - Month of data collection * Day - Day
 of data collection * Time - Time of day of data collection * Location -
 Name of transect, assigned based on the nearest town to the transect *
 Site - Name of logger location within a transect * Distance_m - Distance
 of Site from Lake Superior's shoreline, provided in metres * Exposure
 - refers to exposure of shoreline of associated transect. Exposed shores
 do not have offshore islands buffering them from high winds and waves,
 while unexposed sites are protected by offshore islands. * Temp -
 temperature reading for associated date and time. Data is provided in °C
 2. Missing data codes: NA 3. Specialized formats or other abbreviations
 used: None
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: Hillman_Mean daily temperatures.csv 1.
 Variable List: * Location - Name of transect, assigned based on the
 nearest town to the transect * Site - Name of logger location within a
 transect * Year - Year of data collection * Date - Date of data
 collection, provided in month/day/year * Distance_m - Distance of Site
 from Lake Superior's shoreline, provided in metres * Exposure -
 refers to exposure of shoreline of associated transect. Exposed shores do
 not have offshore islands buffering them from high winds and waves, while
 unexposed sites are protected by offshore islands. * mean.temp - Mean
 daily temperature, provided in °C 2. Missing data codes: NA 3. Specialized
 formats or other abbreviations used: None
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: Hillman_site differences.csv 1. Variable
 List: * Location - Name of transect, assigned based on the nearest town to
 the transect * Site - Name of logger location within a transect * Year -
 Year of data collection * Date - Date of data collection, provided in
 month/day/year * Distance_m - Distance of Site from Lake Superior's
 shoreline, provided in metres * Exposure - refers to exposure of shoreline
 of associated transect. Exposed shores do not have offshore islands
 buffering them from high winds and waves, while unexposed sites are
 protected by offshore islands. * mean.temp - Mean daily temperature,
 provided in °C * temp_100 - Mean daily temperature of each transect's
 associated 100 km reference logger, provided in °C * temp_diff -
 Difference in temperature between mean.temp and temp_100 * elevation -
 Elevation of each logger site above the lake surface, provided in metres *
 elev_100km - Elevation of each transect's associated 100 km reference
 logger, provided in metres * elev_diff - difference in elevation between
 elevation and elev_100km * shore_width - width of shoreline adjacent to
 the 10 m logger of each transect, determined as the distance in metres
 from the water's edge to continuous treeline. * depth_neg - Average
 depth of water within 10 km of shore, for each transect. Values are
 negative to reflect depth. Provided in metres * offshore_temp - Average
 surface water temperature within 10 km of shore, for each transect.
 Provided in °C * latitude - Latitude of each site 2. Missing data codes:
 NA 3. Specialized formats or other abbreviations used: None
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: Hillman_met station differences.csv 1.
 Variable List: * Location - Name of transect, assigned based on the
 nearest town to the transect * Site - Name of logger location within a
 transect * Year - Year of data collection * Date - Date of data
 collection, provided in month/day/year * Distance_m - Distance of Site
 from Lake Superior's shoreline, provided in metres * Exposure -
 refers to exposure of shoreline of associated transect. Exposed shores do
 not have offshore islands buffering them from high winds and waves, while
 unexposed sites are protected by offshore islands. * mean.temp - Mean
 daily temperature, provided in °C * temp_100 - Mean daily temperature of
 each transect's associated 100 km reference logger, provided in °C *
 temp_diff - Difference in temperature between mean.temp and temp_100 *
 temp_met - Mean daily temperature of nearest meterological station,
 provided in °C * met_diff - Difference in temperature of between mean.temp
 and temp_met 2. Missing data codes: NA 3. Specialized formats or other
 abbreviations used: None
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: Hillman_disjunct_prop.csv 1. Variable List:
 * Location - Name of transect, assigned based on the nearest town to the
 transect * Site - Name of logger location within a transect * Year - Year
 of data collection * Date - Date of data collection, provided in
 month/day/year * Distance_m - Distance of Site from Lake Superior's
 shoreline, provided in metres * Exposure - refers to exposure of shoreline
 of associated transect. Exposed shores do not have offshore islands
 buffering them from high winds and waves, while unexposed sites are
 protected by offshore islands. * mean.temp - Mean daily temperature,
 provided in °C * temp_100 - Mean daily temperature of each transect's
 associated 100 km reference logger, provided in °C * temp_diff -
 Difference in temperature between mean.temp and temp_100 * elevation -
 Elevation of each logger site above the lake surface, provided in metres *
 elev_100km - Elevation of each transect's associated 100 km reference
 logger, provided in metres * elev_diff - difference in elevation between
 elevation and elev_100km * shore_width - width of shoreline adjacent to
 the 10 m logger of each transect, determined as the distance in metres
 from the water's edge to continuous treeline. * depth_neg - Average
 depth of water within 10 km of shore, for each transect. Values are
 negative to reflect depth. Provided in metres * offshore_temp - Average
 surface water temperature within 10 km of shore, for each transect.
 Provided in °C * latitude - Latitude of each site * prop_disj - proportion
 of total species at each shoreline site that are considered to be disjunct
 arctic-alpine species * gdd - Growing Degree Days above base temperature
 threshold of 0°C, calculated for the growing season of April 1 - Sept 30,
 2019 * thresh_days - Average number of days per year 2. Missing data
 codes: NA 3. Specialized formats or other abbreviations used: None
 \#########################################################################
 DATA-SPECIFIC INFORMATION FOR: Hillman_GDD_all.csv 1. Variable List: *
 Location - Name of transect, assigned based on the nearest town to the
 transect * Site - Name of logger location within a transect * Distance_m -
 Distance of Site from Lake Superior's shoreline, provided in metres *
 gdd0 - Growing Degree Days above base temperature threshold of 0°C,
 calculated for the growing season of April 1 - Sept 30, 2019 2. Missing
 data codes: NA 3. Specialized formats or other abbreviations used: None