The document analyzes temperature data collected hourly from 1992 to present at multiple depths from 3 coastal sites around Santa Catalina Island, California. It finds that the sites have similar seasonal temperature trends with hottest months from July to September and coldest from December to April. However, the East End and Little Harbor sites experienced greater variability likely due to stronger ocean currents. The high-resolution temperature data set will be publicly available and provides important context for biological research in the region.

1. Background
Discussion
HOURLY TO INTERANNUAL IN SITU SEA TEMPERATURE VARIABILITY AT MULTIPLE
COASTAL OCEAN SITES AROUND CATALINA ISLAND, CALIFORNIA
Melissa Abderrahim1, Diane Kim2 ,Thomas W. Turney3
1McGill University, 2University of Southern California and the USC Wrigley Institute for Environmental Studies
3Wrigley Institute for Environmental Studies-Catalina Conservancy Divers
Available Data
Analysis of temperature data at 3 sites
Table 1. Summary of study sites, depths and available dates (*note: some missing time points). Temperature data from sites in bold
were used for comparative analysis. Results can be found in the section ‘Analysis of temperature data at 3 sites’.
Figure 6. Monthly averages of sea temperature (15 feet) at WIES, East End and
Little Harbor between 1992 and 2011 (plotted with standard error bars). The three
sites display similar seasonal trends, but East End displayed the highest amount
of interannual variability, particularly for the months of January, February,
March, November and December. Warmest months were between July and
September (averages of ~18->20 °C), while coolest moths were found between
December and April (averages of ~14-15 °C).
Figure 5. Hourly sea temperature data (15 feet) collected at WIES, East End and
Little Harbor on May 24th 2006. Temperature at WIES is 18°C at the beginning of
the day and remains stable until 11:00, increasing by less than 1°C) from noon to
15:00, before slowly decreasing throughout the rest of the afternoon and evening.
The temperature at the East End site begins much lower, at 15.7°C and increases to
~17.5°C and stabilizes from 7:00 to 20:00, before dropping back to 16°C at 21:00
and 15.7°C by the end of the day. Little Harbor starts at 15.2°C and experiences a
small variability throughout the morning until it rapidly increasing to 17°C by 9:00.
The temperature then drops to 14.6°C at 15:00 and increases again in the evening
to reach the highest temperature of the day (17.4°C) at 23:00.
Methods
The scientific divers deployed and retrieved HOBO Tidbit v2 temperature loggers (Figure 3) at 6 coastal ocean sites
around Catalina Island from 1992 and the present. Temperature loggers were deployed for several months up to a couple
of years at a time, collecting hourly temperature data. HOBO Tidbits were deployed at several depths for most sites
(Table 1) and replicate loggers were deployed to ensure accuracy, when possible. Once the loggers were retrieved, the
data was downloaded as an excel or text file and organized by site, depth and sampling date. Sea surface temperature data
was also downloaded from NOAA’s Coast Watch site (GHRSST satellite) for the Wrigley Institute’s location and used as
a comparative data set to the HOBO temperature data.
Fig.3 Onset UTBI-
001 TidbiT v2
Temperature logger
Figure 2. Map of Southern California and the Channel Islands
with surface currents recorded on July 22, 2015. (cred: Google Earth)
Figure 1. Map of Santa Catalina Island and the study sites.
(cred: Google Earth)
References
NOAA Coast Watch. 2015. National Oceanic and Atmospheric Administration; [cited on Jul 30th, 2015]. Available from: http://coastwatch.pfeg.noaa.gov/erddap/griddap/erdGRssta1day.graph
Surface Current Mapping. 2015. Southern California Coastal Ocean Observing System. [cited on Jul 30th, 2015]. Available from: http://www.sccoos.org/data/hfrnet/
environmental science, and by fostering an understanding of the natural world among people of all ages. At the Wrigley
Institute, scientists investigate biological adaptations to climate change, study interactions among humans and natural
systems, and connect science to environmental policy. The Wrigley Institute maintains a marine field station on Catalina
Island (the USC Philip K. Wrigley Marine Science Center) for affiliated faculty and researchers to conduct environmental
studies. Since 1992, WIES has collaborated with WIES-CC (Wrigley Institute for Environmental Studies-Catalina
Conservancy) scientific divers to collect biological and environmental data from multiple coastal ocean sites around
Catalina Island, CA (Figure 1). Catalina Island’s coastline is dotted with marine protected areas and areas of biological
significance, serving as important sites for research and education. Here, we present a database and analysis of long-term in
situ temperature data collected by the scientific divers from different sites around Catalina Island, CA that will help better
inform researchers and educators about the natural ecosystems surrounding the island.
The mission of the USC Wrigley Institute for Environmental Studies (WIES) is to encourage
responsible and creative decisions in society by providing an objective source of marine and
• The data set presented here provides insight into interannual, seasonal and diel patterns in temperature at coastal
ocean sites around Santa Catalina Island (Figures 1-2, 4-6).
• Data will be publicly available through the Wrigley Institute’s Online Data Portal (under development) for researchers
and educators. Data will also be used to provide important contextual information for biological data collected as a
part of the WIES-CCD research program.
• Temperature derived from NOAA Coast Watch (GHRSST satellite) is consistent with temperatures in our data set
(Figure 4), corroborating the accuracy of our data points.
• However, satellite data have spatial and temporal limitations that our data set addresses by providing high temporal
resolution (hourly, Figure 5) and site- and depth-specific logs of temperature around Catalina Island (Table 1).
• The WIES, East End and Little Harbor sites display similar seasonal trends, with hottest months between July and
September and coolest months between December and April (Figure 6).
• East End and Little Harbor experienced greater variability on multiple temporal scales of analysis (Figures 4-6),
presumably due to greater exposure to strong oceanic currents compared to the WIES site (Figure 2). Further quality
control and calibration checks will be made to confirm the accuracy of data trends.
Figure 4. Averages of hourly sea temperature (15 ft) data for each month between 1992 and 2011 (in °C) at the Wrigley Institute for Environmental Studies (WEIS),
East End and Little Harbor sites (see Figure X for map of sites)., at a depth of 15feet. Monthly averages were calculated from the dataset for every year for each site
(according to data availability). Overlaid on the plot is sea surface temperature from satellite data In addition, daily recordings from the using the NOAA CoastWatch
site for Catalina Island, near the Wrigley Institute (only 2006-2011 data were available). Similar seasonal trends were observed at the three different sites, with
temperature ranging between 21°C and 23°C during the warmest times of the year (June to September) and between 13°C to and 15°C during coldest times of the year
(January to March). The years of 1994, 1998, 2006 and 2007 display warmer temperatures between January and March, correlating with El Nino years.
We would like to thank the WIES-CCD divers and the Catalina Conservancy for the data
collection, the Wrigley Institute for Environmental Studies and USC Environmental Studies for
their support.
Acknowledgements
Long-term (1992 to the present) temperature data with high temporal
resolution (hourly) collected at multiple coastal ocean sites around Catalina
Island will be publicly available through the Wrigley Institute’s Data Portal
(under development). The temperature data set includes the sites, depths
and dates indicated in Table 1.
Site Name Coordinates Depths (feet) Dates*
Cat Harbor
33°25'51.36"N
118°30'25.88”W
30 Sep 2006 – Nov 2006
Eagle Reef
33°28'21.99"N
118°36'17.91"W
15, 30, 40, 60
Jun 2006– Sep 2014
East End
33°17'54.67"N
118°18'43.09"W
15, 30, 60
Aug 1995 – July 2013
Little Harbor
33°23'1.40"N
118°28'30.61"W
15, 30, 60
Jul 1993 – Sept 2014
WIES
33°26'39.58"N
118°29'6.75"W
15, 30, 60, 100
Aug 1992 – Aug 2010
West End
33°28'47.35"N
118°36'27.43"W
15, 30, 60, 40
Oct 1993 – Jul 2006