Chapter 16
Ocean ecology and global climate change
The phrase “global climate change” has long since become a mantra chanted by Earth
scientists before international boards and national legislatures as we seek to influence
environmental policy and to generate research support. A wide range of issues is
involved in this chanting, and their advocates compete for attention and money.
Biological processes in the ocean have a part in some climate control mechanisms,
and changed climate will affect marine life. Thus, climate change and its effects have
become a significant part of biological oceanography. Change has become
synonymous with warming, and global warming of the atmosphere and oceans,
relative to mid-20th-century temperatures, is definitively upon us. The subject is
sufficiently complex that the United-Nations-sanctioned Intergovernmental Panel on
Climate Change (IPCC) required four weighty volumes to cover it in their 2007
report, now already outdated. The best we can do in a single chapter is outline how
biological processes in the ocean may affect climate on long time scales, show how
ocean climate varies on decadal time scales, and give some examples of the plethora
of effects of warming.
(^) Climate has never been constant on the Earth. Shifts in mean temperature;
temperature-cycle amplitude; precipitation rate; snow versus rain; seasonal snowfall
and ice melting; evaporation; and length of growing season, are among the most
important driving forces for evolution. At present, during an interglacial period, we
are in a reasonably favorable climate compared to much of the Pleistocene era, and
even compared to the 17th to 19th centuries. The 20th century saw mostly moderate
conditions, gradual warming and long growing seasons compared to the few previous
centuries. Since the 1980s, warming has been a source of serious and public concern,
and warming promises to remain an important issue for the foreseeable future. Not
only is the climate changing, the present distribution of climates over the Earth is
coupled to the means for feeding and sheltering ∼6.9 billion people (February 2011),
more than four times the population of only 100 years ago. It is reasonable to think we
are dependent upon climate conditions certain to change.
(^) Thus, we are right to be worrying about the retreat of montane glaciers; melting of
the Greenland and antarctic ice sheets; summertime loss of Arctic Ocean sea ice;
poleward shift of malarial mosquitoes; enhanced intensity of short-term climate cycles
like the El Niño–Southern Oscillation; changes in rainfall quantities and distribution;