Journal of Geophysical Research: Oceans
Supporting Information for
Decadal and seasonal changes in temperature, salinity, nitrate and chlorophyll in inshore
and offshore waters along southeast Australia
Paige Kelly, Lesley Clementson and Vincent Lyne
CSIRO
Contents of this file
Text S1 to S2
Figures S1 to S2
Additional Supporting Information (Files uploaded separately)
N/A
Introduction
The following supporting information been included to clarify two methods used in this study;
the analysis of 1o Longitude by 0.5 o Latitude boxes of chlorophyll-a (S1), and the decadal
analysis of the Maria Island and Port Hacking time series (S2). The data analysed in the
supporting information are median filtered satellite derived chlorophyll-a from 1997-2012 at
Port Hacking (34.1°S, 151.3°E) and Maria Island (42.6°S, 148.2°E), and temperature data
recorded at Maria Island from 1950-2012. The supporting information are figures produced in R.
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Descriptions of the relevant statistical processes are provided below, and complete details of
the datasets are provided in the corresponding manuscript.
Text S1.
To determine a suitable box length, the spatially lagged correlations from Maria Island and Port
Hacking were computed from the yearly ocean color satellite images. Transects two longitude
degrees in length were extended out from each of the stations and cross-correlations were then
computed between yearly values at the station and values out along the transect. An eastward
and a southward transect were used to produce the trends by longitude and latitude
respectively. Both stations showed reasonably consistent drop-offs in correlations with lag out
to about 0.5o, and less consistent drop-offs out to 1o (Figure S1). Beyond these lags, correlations
were inconsistent, erratic or appeared to have an increasing trend, which we took to indicate
the presence of large-scale patterns (such as the EAC offshore of Port Hacking apparent in the
Longitude Transect). Taking into consideration these trends, and the fact that we couldn't
extend too far north in latitude without approaching land, a box length of 1o was chosen as a
reasonable size for longitude, and 0.5o for latitude.
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Figure S1. Lagged cross-correlations computed for Maria Island and Port Hacking from the
yearly ocean color satellite images. Each yearly image was the median filter of the monthly
images for that year. Cross-correlations were computed between the pixel value at the
station and pixels extending out offshore from the same latitude (a) and south (b).
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Text S2.
To examine temporal variations at the long-term stations over a finer time period than the
entire time series, lagged correlations of temperature and ocean color were computed at Maria
Island to determine the timescale over which yearly temperature signals persisted, or were lagcorrelated. Choosing a time period over several lag-correlation time periods would ensure that
changes across these time periods were due to variations that were longer term than the
correlation period. Yearly temperature for Maria Island was computed from the long-term
station record analysed in this study (1950 - 2008) and yearly ocean color was computed from
the satellite ocean color data at the location of Maria Island (1998 - 2012). The lagged
correlations (Figure S2) drop to below, or near, the level of significance after lags of one and
two years. The temperature shows a slight significance at two years lag, whereas the ocean
color is significant at a lag of one year and just below significant at a lag of two years. Note also
that the temperature correlation returns to just below significant at a lag of 11 years. These
observations suggest that a decadal time period would be several times the lag correlation time
scale (or approximately two years) and less than a weak longer period correlation of 11 years
suggested by the temperature correlations. Taking these into consideration, we chose a
decadal time period as appropriate to examine longer-term changes at the monitoring stations.
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Figure S2. Lagged cross-correlations computed for the Maria Island station (42.6°S, 148.2°E)
from the yearly satellite ocean color data (1998 - 2012, a) and from the yearly long-term
temperature record (1950 – 2008, b). The yearly temperature was computed as an average,
whereas the ocean color was an average of the median monthly value at 42.6°S, 148.2°E.
The dotted horizontal lines represent the confidence intervals for the correlations.
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