Transcript The pace and scope of climate change

YOUR OUTLINES?
EXAM 2?
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?? -> what is the latest news??
COASTAL ZONES AND MARINE
ECOSYSTEMS
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Chapter 6, IPCC (2001)
OCEANS: SO WHAT?
70% of the Earth’s surface
 Regulate the Earth’s climate
 Modulate the global biogeochemical cycles
 Supplies of resources and products worth trillions
of dollars each year
 Function as areas of recreation and tourism,
medium for transportation, repository of genetic
and biological information, sinks for wastes
(these functions are also shared by the coastal
margins of the oceans)
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HUMANS AND OCEANS
~ 20% of the world’s human population live w/in
30 km of the sea; ~ 40% live w/in the nearest 100
km of the coast
 600 million people will occupy coastal floodplain
land below the 1,000-year flood level by 2100
 climate change will affect the physical,
biological, and biogeochemical characteristics of
the oceans and coasts at different time and space
scales  positive feedback on the climate system
 Note: the oceans already under stress. From
what? Consequence of this stress?
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?: what are the potential impacts of climate
change on the coastal zone, marine ecosystems,
and marine fisheries
 First: what do we know
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STATE OF KNOWLEDGE
Global warming will affect the oceans through
changes in sea-surface temperature (SST), sea
level, ice cover, ocean circulation, and wave
climate
 Ocean conveyor belt -> global ocean thermohaline
circulation system; emphasizes the role of the
global ocean as a climate regulator
 Projections:
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SST-induced shifts in the geographic distribution of
marine biota and changes in biodiversity,
particularly in high latitudes
 Decrease in ice-infested waters
 Sea-level changes from thermal expansion
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STATE OF KNOWLEDGE: LOW CERTAINTY
Changes in the efficiency of carbon uptake
through circulation and mixing effects on
nutrient availability and primary productivity
 Changes in ocean uptake and storage capacity for
GHG
 Potential instability in the climate system caused
by freshwater influx to the oceans and weakening
of the ocean conveyor belt
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MARINE ECOSYSTEMS:
A general warming of a large part of the world
oceans during the past 50 years
 Overall increase associated with land-based
global temperature trends
 Global mean sea-level has risen by about 0.1–0.2
mm yr-1 over the past 3,000 years and by 1–2
mm yr-1 since 1900, with a central value of 1.5
mm yr-1
 Suggested: maximum intensity of tropical
cyclones may rise by 10-20%; might persist for
longer time due to increased SST
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OCEAN CONVEYOR BELT….
Role in controlling the distribution of heat and
GHG
 Circulation: driven by differences in seawater
temperature and salinity
 Some evidence: will weaken (Slow down? Stop?)
due to climate change
 (more on this later)
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MARINE ECOSYSTEMS: SEA ICE…
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11% of the ocean (seasonal)
Affects:
salinity
 ocean-atmosphere thermal exchange
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Determining the intensity of convention in the ocean, and thus
the mean time scale of deep-ocean processes affecting carbon
dioxide update and storage
Changes
Large reductions in the extent, thickness and duration of
sea ice
 Already: significant decrease in spring and summer sea-ice
by ~ 10-15% since the 1950s in the northern hemisphere;
 may be underestimated due to significant thinning of sea
ice in the Arctic; may be as much as 25%between 1950s1970s
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MARINE ECOSYSTEMS: BIOLOGICAL
PROCESSES
Can sequester CO2 and remove carbon to the
ocean interior: biological pump
 Rise in temperature  faster biodegradation +
faster dispersal of global organic pollutants …
 Photosynthesis (the major process by which
marine biota sequester carbon dioxide) –
controlled by the availability of nutrients and
trace elements (eg: iron)
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Climate change could affect the inputs of nutrients
and iron to the ocean…
 Greatest impact in semi-enclosed seas and bays
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ALSO…
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CC can shift structure of biological communities
in the upper ocean…. Change stratification…can
impact the biological bump…
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MARINE ECOSYSTEMS: MARINE CARBON
DIOXIDE UPTAKE
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Oceans: ~ taken up 30% (great uncertainty) of carbon
dioxide emissions between 1980 and 1989
How?
Burial of organic carbon in marine sediment ->
removing atmospheric carbon dioxide for prolonged
time periods
But…
If CC could reduce ability to carbon uptake
(latest news: you tell me)
Also: weakening the conveyor belt -> reduce ocean’s
ability to absorb carbon dioxide
With a doubling of CO2 scenario, ocean uptake of
CO2 dropped by 30% over a 350-yr period
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MARINE ECOSYSTEMS: MARINE FISH
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Because climatic factors affect the biotic and abiotic
elements -> they influence the numbers and distribution of
fish species
What are the abiotic factors?
Water temperature
Salinity
Nutrients
Sea level
 Amount of sea ice
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And the biotic factors?
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Food availability
Presence and species composition of competitors and predators
Water temperature directly impacts
Spawning and survival of larvae and juveniles, and fish
growth
 Biological production rate -> food avalability
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MARINE ECOSYSTEMS: MARINE FISH
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Variations (with cycles of 10-60 yrs) in the
biomass volume of marine organisms depend on
sea temperature and climate
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Eg: fishing for cod in the Atlantic Ocean – clear
correlation between water temp and catch
Thus: important to consider the ecosystem
impacts of climate variations + changes for
individual species
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MORE ON MARINE FISH
Herrings, sardines and anchovies: shortlived
species that mature at an early age
 Large fluctuations in abundance – associated
with changes in the climate-ocean environment
 Most fishing regime changes can be related
directly to sea-temperature changes, but changes
in other physical attributes also can have an
impact.
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Example: a decrease in wind stress o f Tasmania that
reduced large zooplankton production a ff e c ted the
density of Jack mackerel, which eliminated the
possibility of a commercially viable mackerel fishery
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As ecosystems change, there may be impacts on the
distribution and survival of fishes.
Any changes in natural mortality would be associated
with increased predation and other factors such as
disease.
Improved growth in the early life stages would
improve survival, whereas decreased growth could
facilitate increased mortality.
cautious acceptance that climate change will have
major positive and negative impacts on the
abundance and distribution of marine fish.
Fishing impacts may be particularly harmful if
natural declines in productivity occur without
corresponding reductions in exploitation rates.
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MARINE MAMMALS AND SEABIRDS
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Sensitive indicators of changes in ocean environments
Fluctuations in marine bird and mammal populations in
the North Pacific may be entirely related to climate
variations and change
Climate variations since 1990 + overfishing  behavioral
changes in killer whales  reduced sea otter abundance 
changed the ecology of the kelp forests
The changes in prey resulting from persistent changes in
climate appear to be one of the important impacts of a
changing climate on the marine mammals that feed from
the top of the food chain.
CC  effect access to prey among marine mammals
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Eg: ice-free seasons in the Arctic  prolong fasting of polar
bears…
Reductions in sea ice have been predicted to alter the
seasonal distributions, geographic ranges, migration
patterns, nutritional status, reproductive success, and
ultimately the abundance of Arctic marine mammals
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SEABIRDS
May consume vast amounts of fish (600,000 t/yr
in the North Atlantic; 20-30% of the annual
pelagic fish production)
 Hard to distinguish CC from overfishing
 How likely is it to survive?  depends on its
ability to alter its migration strategy
 Long lifespans and genetic variation within
populations enable seabirds to survive adverse
short-term environmental events,
 However, small populations tied to restricted
habitat, such as the Galapagos Penguin may be
threatened by long-term climate warming
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DISEASES AND TOXICITY
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Changes in precipitation, pH, water temperature,
wind, dissolved CO2, and salinity can affect
water quality in estuarine and marine waters.
Some marine disease organisms and algal species are
strongly influenced by one or more of these factors
 increase in reports of diseases affecting closely
monitored marine organisms, such as coral and
seagrasses, particularly in the Caribbean and
temperate oceans
 several viruses, protozoa, and bacteria affected by
climatic factors can affect people, by direct contact or
by seafood consumption.
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Example: bacterium found in oysters; cholera epidemics
associated with marine plankton
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COASTAL SYSTEMS
Existence of many depends on the land-sea
connection
 Wide range of environmental conditions:
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Salinity (fresh to hypersaline)
Energy (sheltered wetlands to energetic wave-washed
shorelines)
Spectrum of climate types: tropical to polar
Exposed to land-source and marine hazards, waves,
river flooding, shoreline erosion, biohazards (algal
blooms and pollutants) …
Know Box 6.3 and Box 6.4
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COASTAL SYSTEMS
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Beaches, Barriers, Cliff Coasts
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More erosion with CC likely; changes in wave or storm patterns…
What about presence/absence of biotic protection such as
mangroves?
Deltaic Coasts (low-lying coastal regions)
Exposed to potential flooding
Nile: significant land loss can result from wave erosion; also: large
portions of the Amazon
 Saltwater intrusion into freshwater aquifers
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Coastal Wetlands
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By 2080, sea-level rise  loss of 22% of world’s coastal wetlands
(mangrove forest and salt marsh); much already lost
Tropical Reef Coasts
More than 25% of all known marine fish + food source; 58% at
risk from human activities. Global CC could be an additional
cause
 Sea-level rise + increased carbon dioxide levels + temperature…
 Latest news…
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High-Latitude Coasts (ice-rich coasts)
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LATEST NEWS
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Based on current model
simulations, the
Meridional Overturning
Circulation (MOC) of
the Atlantic Ocean will
very likelyslow down
during the 21st century;
nevertheless
temperatures over the
Atlantic and Europe are
projected to increase.
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