International Polar Year 2007–2008 - WMO

3.3 Southern Ocean Observing System
Lead Authors:
Steve Rintoul and Eberhard Fahrbach
Reviewers:
Ian Allison, Colin Summerhayes and Tony Worby
Historically, the Southern Ocean has been
one of the least well-observed parts of
the ocean. The Southern Ocean is remote
from population centers and shipping
lanes. Strong winds, large waves and sea ice provide
additional reasons for vessels to avoid the region.
Oceanography is also a young field. At the time of IGY,
studies of the open ocean were rare, particularly in the
Southern Ocean. Systematic circumpolar exploration
of the region was conducted by George Deacon on
the Discovery II in the 1930s, by Arnold Gordon and
colleagues on the Eltanin in the late 1960s and early
1970s, within the framework of the International
Southern Ocean Studies (ISOS) and Polar Experiment-
South (POLEX-South) programs in 1970s-1980s, and
during the World Ocean Circulation Experiment
(WOCE) and Joint Global Ocean Flux Study (JGOFS)
programs in the 1990s. Each of these expeditions
was a major step forward in the exploration and
understanding of the Southern Ocean. However,
each survey suffered from similar weaknesses: each
circumpolar survey took on the order of a decade
to complete, was based on ship transects widely
separated in space and time, and was heavily biased
towards the summer months. A number of important
Southern Ocean biological studies were conducted,
including Biological Investigations of Marine Antarctic
Systems and Stocks (BIOMASS) in the 1980s and
Global Ecosystem Dynamics (GLOBEC) in recent
years, but these efforts tended to focus on particular
regions since a comprehensive circumpolar survey of
the shallow and deep waters around Antarctica was
not technically feasible. Many valuable studies were
conducted as stand-alone investigations, but from
these alone it was difficult to synthesise a circumpolar
view of the status of the Southern Ocean. Satellite data
were however proving increasingly useful for synoptic
studies, and the advent of the Argo profiling float
PA R T T H R E E : I PY OBSERVING SYS T E M S , T H E I R L E G AC Y A N D DATA M A N AG E M E N T
programme around 2003 began to provide useful data
from just below the surface down to 2000m, though
not from areas extensively covered by winter sea ice.
Against this background, IPY was a major leap
forward. The unprecedented level of cooperation
and coordination during IPY – between nations,
disciplines, scientists, logistic providers and communicators
– allowed a synoptic “snapshot” of the
state of the Southern Ocean to be obtained for the
first time. Advances in technology played a huge role
as well, and IPY was well-timed to take advantage
of revolutions in ocean observations and genetic
techniques. New tools like autonomous profiling floats
and miniaturised oceanographic sensors suitable for
deployment on marine mammals have allowed yearround,
broad-scale sampling of the Southern Ocean
for the first time, including the ocean beneath the
sea ice. DNA barcoding and environmental genomics
are providing completely new ways to investigate
evolution and biodiversity, ecosystem function and
biological processes. New cryospheric satellites
provided encouragement that variables of essential
relevance to climate, such as sea ice volume and other
characteristics relevant to air-sea-ice interaction,
might be derived from space-based observations.
New trace-metal clean techniques were developed,
allowing many elements and isotopes to be measured
for the first time throughout the full ocean depth.
IPY was also well-timed because at least some
regions of the Southern Ocean have experienced
rapid change in recent decades. The western Antarctic
Peninsula has warmed dramatically; the duration of
the sea ice cover has decreased near the peninsula at
rates comparable to those observed in the Arctic, and
increased in the Ross Sea; the collapse of ice shelves
has opened up new areas of ocean where the process
of seabed colonisation can be observed; and large
but regionally-varying changes in temperature and
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 385