Auxiliary Material for
Artifacts in variations of ocean heat content induced by the observation system
changes
by L. Cheng1, J. Zhu1
1. International Center for Climate and Environment Sciences (ICCES), Institute of
Atmospheric Physics, Chinese Academy of Sciences, Beijing, China, 100029.
Geophysical Research Letters
Introduction
These auxiliary material files contain supplemental figures, table, references, methods
and discussion that support the main text of the article.
Auxiliary Figures S01-S06.doc: Supplementary figures with captions included.
Auxiliary Material - text01.doc: Present supplementary methods and discussions.
Auxiliary Material - ts01.doc: Present supplementary table.
Fig. S01: Yearly averaged ocean heat content (0-700-m depth-averaged temperature
anomaly) within different regions of the Pacific Ocean (a) and the Atlantic Ocean (b),
showing where the OHC shift occurred in 2001–2003. This figure shows that the
OHC shift during the period 2001–2003 occurred primarily between 20°S and 10°N
in the Eastern Pacific Ocean and between 50°S and 10°N in the Atlantic Ocean,
which is where we detected a pronounced increase in the OHC. The OHC in the
Indian Ocean was not presented because the ocean heat content change was
extremely small in the Indian Ocean.
Fig. S02: Illustration of how the sampling bias is detected. The ocean heat content
(OHC) anomaly is shown for each gridded box over the global ocean in 2004. Dashed
boxes are the regions where the OHC shift was detected (see Fig. S01). The 1966
sampling is masked by grey shading. When using the 2004 OHC as a stationary
ocean, the OHC anomalies in the shaded area were selected and used to calculate a
mean OHC anomaly that was compared to the global mean OHC anomaly calculated
using all of the OHC anomalies in 2004.
Fig. S03: Full and sub-sampled OHC anomaly distributions. The distribution of the
grid-averaged ocean heat content anomaly (in units of degrees centigrade, weighted
by the area of the grid) from 2003 to 2010 (blue) and the distribution when the OHC
was sampled in each year using 2001 horizontal sampling (light red) are shown. The
global means of the two OHC distributions are presented in red (2001 sampling) and
green (full sampling). A cold-biased distribution was found when we sampled the
OHC for each year at the 2001 observation locations.
Fig. S04: The ocean heat content is calculated using the Levitus2012-mapping
method based on the entire dataset (red), subsets after removing the WOCE data
(blue), and subsets after removing the Argo data (dashed light blue). Three different
“influence” distances are also used to calculate the OHC, i.e., 333 km, 222 km and
111 km.
Fig. S05: The ocean heat content estimated for different scenarios. The
depth-integrated strategy is shown, in which temperature anomalies are first averaged
globally at each standard depth and then over the depth (in blue). This method differs
from the strategy used in the current study, in which temperature anomalies were first
averaged over the depth for each grid box and subsequently used to obtain a global
average (in red). The OHC was also calculated by removing the XBT data (in grey).
Fig. S06: Effect of the seasonal bias on the calculated OHC. (a), Monthly mean data
sampling intensity for two time periods: 1966-2001 (red) and 2003-2012 (blue). (b),
Monthly (blue shades) and yearly mean (blue dotted line) of the Niño3.4 index and
yearly mean of the Niño3.4 index weighted by the data volume for each month over
the global ocean (red cross line) and by the monthly data volume for the Southern
Hemisphere (purple square line). The data volume for each month from 1995 to 2008
is shown in orange.
Table S01: The warming rate for the upper 700 m of the ocean over seven time
periods, including 1966–2012, 1980–2012, 1990–2012, 2000–2012, 2004–2012, and
1993–2008, which correspond to the Lyman et al. [2010] estimate; 1969-2008, which
corresponds to the Levitus et al. [2009] estimate; and 1971-2010, which corresponds
to the IPCC-AR5 estimate (Rhein et al. [2013]). The 90% confidence intervals of
each estimate are also presented. The results using the strategy S2 are presented in
this table. The trend estimates are reported as temperature rates, heat content
changing rates, and ocean warming rates averaged over the entire global surface (5.1
× 1014 m2). The results from several independent studies are also presented for
comparison.
References
Abraham, J. P., J. M. Gorman, F. Reseghetti, E. M. Sparrow, and W. J. Minkowycz
(2012a), Drag Coefficients for Rotating Expendable Bathythermographs and the
Impact of Launch Parameters on Depth Predictions, Numer Heat Tr a-Appl,
62(1), 25-43.
Abraham, J. P., J. M. Gorman, F. Reseghetti, E. M. Sparrow, and W. J. Minkowycz
(2012b), Turbulent and Transitional Modeling of Drag on Oceanographic
Measurement Devices, Modelling and Simulation in Engineering, 2012, 8.
Gouretski, V. (2012), Using GEBCO digital bathymetry to infer depth biases in the
XBT data, Deep-Sea Research I, 62, 40-52.
Gouretski, V., and K. P. Koltermann (2007), How much is the ocean really warming?,
Geophys Res Lett, 34(1).