International Polar Year 2007–2008 - WMO

Ocean; and there are indications of ecosystem
changes. However, the short and incomplete nature
of existing time series means that the causes and
consequences of observed changes are difficult to
assess. Sustained, multi-disciplinary observations are
required to detect, interpret and respond to change.
The SOOS will provide the long-term measurements
required to improve understanding of climate change
and variability, biogeochemical cycles and the
coupling between climate and marine ecosystems.
The SOOS includes the following elements:
• Repeat hydrography: Hydrographic sections from
research vessels are the only means of sampling
the full ocean depth. Repeat hydrography provides
water samples for analysis of those properties for
which in situ sensors do not exist, the highest precision
measurements for analysis of change and for
calibration of other sensors, accurate transport estimates
and a platform for a wide range of ancillary
measurements. The location of the recommended
repeat sections is shown in Fig. 3.3-1. On each transect,
measurements will be made of temperature,
salinity, velocity, oxygen and oxygen-18, nutrients,
components of the carbon system, tracers and a
wide range of biological measurements (eg biooptics,
primary production, phytoplankton pig-
Fig. 3.3-2. Present
status of Argo float
array in the Southern
Ocean. Note that
coverage decreases
with increasing
latitude, with few
observations in the
sea ice zone.
Provided by Mathieu Belbeoch
of JCOMMOPS
ments, net tows and acoustics). Trace elements and
isotopes will be measured on some sections.
• Underway sampling from ships: The full hydrographic
sections need to be complemented by
more frequent underway sampling transects, to
reduce aliasing of signals with time-scales shorter
than the 5-7 year repeat cycle of the repeat hydrography.
Measurements will be made of temperature
and salinity (both at the surface and below the surface
using expendable profilers), nutrients, carbon,
phytoplankton and, on some vessels, velocity.
• Enhanced Southern Ocean Argo: Year-round,
broad-scale measurements of the ocean are needed
to address many of the key science challenges in the
Southern Ocean. These measurements can only be
obtained using autonomous platforms like profiling
floats. A sustained commitment to maintain and
enhance a profiling float array in the Southern Ocean
is critical. Argo has made a particularly significant
contribution in remote areas like the Southern
Ocean, where few ship observations exist (Fig. 3.3-
2). Modified Argo floats are needed to obtain data
from beneath the winter sea ice.
• Time-series stations and monitoring of key
passages: Several key passages and boundary
currents in the Southern Ocean are high priorities
o b s e r v I n g s Y s t e m s a n d d a t a m a n a g e m e n t 387