Climate Change and Biodiversity

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Climate Change and Biodiversity
The Arctic
ENVI 5048 Climate Change and Biodiversity Wednesda
y October 10, 2007 Nicole Senyi
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Articles Reviewed

• Tynan, Cynthia T. and DeMaster Douglas P.
  Observations and Predictions of Arctic Climatic
  Change Potential Effects on Marine Mammals.
  ARCTIC VOL. 50, NO. 4 (December 1997) P. 308 322
• Cressey, Daniel. Arctic Sea Ice at Record Low.
  Nature, published online 18 September 2007.
  http//www.nature.com/news/2007/070917/full/news07
  0917-3.html

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Observations and Predictions of Arctic Climatic
Change Potential Effects on Marine Mammals
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Outline

• Introduction
• Changes in Air and Sea Surface Temperature
• Changes in Salinity
• Sea Level Pressure
• Changes in Arctic Sea Ice Extent
• Present Monitoring of the Physical Environment
• Potential Effects on Marine Mammals
• Ice as an Important Substrate for Pinnipeds and
  Polar Bears
• Linkages between Ice and Cetaceans
• Importance of the Ice Edge and Sea Ice Community
  to Marine Mammals
• Migrations and Movements of Marine Mammals
  Relative to the Annual Ice Cycle
• Linkages between Changes in the Freshwater Budget
  and Marine Mammals
• Conclusion

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Introduction

• Purpose of Article
• To give a survey of current model predictions
  (general circulation models or GCMs) of Arctic
  climate warming, and decreased ice in the Arctic
  ocean from the past 30 years
• To highlight the anticipated impact on marine
  mammals in the face of climate change predictions
  and suggest that this information be used to
  support the existence of climate change
• Advise precautionary approaches to high-latitude
  ecosystems management until specific responses of
  Arctic species to complex regional air-sea ice
  dynamics, ocean circulation, and production have
  been determined.
• Main Points
• Climate change in the Arctic Ocean and subpolar
  seas are nonuniform this makes management more
  difficult
• There is a need for monitoring of sea ice extent
  and seasonal distribution of indicator species -
  bowhead whale, ringed seal and the beluga
• Polar Amplification - warming climate is
  amplified by the poles due to the complex
  snow-sea-ice albedo
• Evidence of decreasing Arctic sea ice due to
  warming trends for the past 20-30 years
• Changes in the extent and thickness of Arctic sea
  ice influence global climate by
• 1) altering the surface albedo and radiative
  balance and
• 2) affecting the thermohaline circulation of the
  North Atlantic.

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Source http//scienceblogs.com/islandofdoubt/2007
/08/whalewatching_bad_news_and_goo.php And
http//www.paulnicklen.com/Galleries/MarineMammals
/
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Geography - The Arctic Ocean and Subpolar Seas
Bering Sea (1) Bering Strait (2) Chukchi Sea
(3) Beaufort Sea (4) East Siberian Sea (5) Laptev
Sea (6) Kara Sea (7) Barents Sea (8) Fram Strait
(9) Greenland Sea (10) Iceland Sea (11) Norwegian
Sea (12) North Sea (13) Labrador Sea (14) Davis
Strait (15) Baffin Bay (16)
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Changes in Air and Sea Surface Temperature

• GMCs predict polar amplification of warming due
  to complex interactions between temperature,
  water vapor, and snow-sea-ice albedo feedbacks
• They also predict a reduction of Arctic sea ice,
  a reduction of surface albedo, and consequently
  an increased surface absorption of solar energy
• Surface air temperatures to warm 45C over the
  Arctic and northern seas by the middle of the
  next century
• Increased thermal expansion of the oceans and
  melting of ice are expected to increase the
  global mean sea level by 1595 cm by the year
  2100
• SSTs expected to warm by 0.51.0C by the middle
  of the next century
• Warming is projected to be nonuniform SST should
  increase less in the higher latitudes (Arctic and
  Atlantic Ocean south of Greenland) then the lower
  latitudes due to the heat needed in melting or
  freezing Arctic sea ice and potential for deep
  vertical mixing
• Increased freshwater flows into the North
  Atlantic could potentially alter this expected
  warming by
• Capping the surface layer
• Reduce deep vertical mixing and formation of
  North Atlantic Deep Water
• Substantially reduce the thermohaline circulation
  in the North Atlantic

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Polar Amplification of Warming
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Changes in Salinity

• Increased precipitation and continental runoff
  predicted for high latitudes due to increase in
  CO2 (at a rate of 0.5-1.0 m per year)
• This increase in freshwater drainage may alter
  salinity in oceans and affect ice extent
  (increase or decrease) and cause ice anomalies
• Example Great Salinity Anomaly (GSA) of
  196882, led to the advective freshening of the
  surface layer in the subpolar North Atlantic
  which appears to have caused sea ice anomalies in
  the Greenland Sea, and later in the Labrador Sea
• This change in salinity is thought to have caused
  the Halocline catastrophe where the freshening of
  the oceans due to deglaciation may have shut down
  the thermohaline circulation of the North
  Atlantic
• Changes is salinity may decrease sea ice through
  the reduction of stratification and increase of
  the upward flux of heat from the warm sub-surface
  Atlantic layer
• Models predict a decrease in salinity for the
  Arctic region. This decrease in salinity is due
  to an excess of precipitation over evaporation at
  high latitudes.
• This could decrease ice formation as ice
  formation is dependent on the presence of a
  low-salinity layer
• This decrease could also make the thermohaline
  circulation of the North Atlantic weaker and
  shallower

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Sea Level Pressure

• Period between 1988-1994 was characterized by
  seven years of negative sea level pressure
  anomalies
• During this period the sea level pressure
  anomalies were higher in the central Arctic then
  anywhere else in the Northern Hemisphere
• These anomalies have been linked to cyclone
  activity (closed low pressure systems)
• Sea level pressure controls the movement of sea
  ice, therefore any change in pressure will change
  distribution and movement of sea ice

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Changes in Arctic Sea Ice Extent

• GCMs predict substantial decreases in both
  coverage and thickness of Arctic sea ice in
  response to greenhouse gas-induced warming
• In the period between 1961-1990 from July to
  September an ice loss rate of 9 per decade has
  been observed
• Reductions of Arctic ice extent are nonuniform
  and depend regionally on several complex factors
  freshwater discharge from rivers, salinity
  anomalies, strength and location of atmospheric
  pressure systems, and resultant wind direction
• I.e. ice extent can grow in one area and decrease
  in an other while the overall sea ice extent
  decreases
• Since 1979 there has been a steady decline in
  Arctic summer ice coverage
• Plus each year the rate of decrease grows
• Greatest reduction of sea ice monitored occurred
  in Siberia
• May be premature to rule out the possibility of
  natural climate change

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Present Monitoring of the Physical Environment

• Modern climatic data are derived largely from
  drifting buoys, satellites, and land-based
  stations
• These monitor temperature, SST, surface pressure,
  and sea ice data
• Some data sources
• Climate Research Unit of the University of East
  Anglia
• North Pole drifting ice stations
• Comprehensive Ocean-Atmosphere Data Set
• U.S. Navy-National Oceanic and Atmospheric
  Administration Joint Ice Center
• Polar Science Center at the University of
  Washington (most accurate)
• Some technologies employed
• Scanning Multichannel Microwave Radiometer (SMMR)
• Special Sensor Microwave/Imager (SSM/I)
• For the most part data coverage is uneven and few
  records exist for polar regions
• Continued monitoring is crucial to establish
  long-term trends

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Potential Effects on Marine Mammals

• Some of the effects of climate change on marine
  mammals include
• Loss of ice (habitat)
• Pray availability and therefore nutrition
• Reproduction
• Geographic range
• Migration patterns

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Potential Effects on Marine Mammals

• Ice as an Important Substrate for Pinnipeds
• and Polar Bears

• Both mammals are affected by change in
  ice-associated habitat
• Pinnipeds
• Seals depend on pack-ice habitat for pupping,
  foraging, moulting, and resting
• Ringed seals depend on stability of ice for their
  young
• Bearded seals and walruses require thin or broken
  ice cover over shallow water to forage
• Population distributions, densities, and foraging
  patterns are all dependant on suitable sea ice
  conditions
• Polar Bears
• Require sold substrate on which to hunt ringed
  seals
• Changes in extent and type of ice cover will
  affect population distributions and hunting
  patterns
• As well, any decline in seal populations will
  negatively affect polar bear populations
• Once ice melts in the southern extent of the
  polar bear's habitat they fast for the summer.
  Earlier ice melts could adversely affect the
  bear's nutrition

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Potential Effects on Marine Mammals

• Linkages between Ice and Cetaceans

• Loss of sea ice to cetaceans (whales) may relate
  more to prey availability then to habitat
• Loss of ice may lead to population redistribution
• Bowhead whale population and distribution may be
  influenced by ice cover and feeding opportunities
  and in a warmer Arctic this distribution may
  change
• The narwhal and beluga forage at ice edges and
  cracks, therefore loss of sea ice would affect
  them more directly
• International Whaling Commission (IWC) considers
  the following Arctic species or populations to be
  potentially more vulnerable than other species of
  cetaceans
• Eastern Arctic bowhead whale
• Okhotsk
• Sea bowhead whale
• All stocks of beluga whale
• All stocks of narwhal

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Potential Effects on Marine Mammals

• Importance of the Ice Edge and Sea Ice
• Community to Marine Mammals

• Ice edge production (algae, phytoplankton, etc)
  is crucial to the food supply of other Arctic
  mammals
• Ice algae plays an important role in supporting
  the Arctic ice edge ecosystem, especially the
  Arctic cod
• Cod is an integral part of the Arctic food web,
  providing belugas, narwhals, harp seals, ringed
  seals, bearded seals, and hooded seals with their
  primary food source
• The mouth of the artic cod is adapted to
  under-ice feeding
• Regional changes in the extent of sea ice may
  lead to redistributions of Arctic cod, and
  consequently to redistributions and altered
  migration patterns of marine mammals.

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Potential Effects on Marine Mammals

• Importance of the Ice Edge and Sea Ice
• Community to Marine Mammals

• Algae production and in turn phytoplankton bloom
  is closely tied with the spring breakup of ice
• Colder temperatures increases nutrient supply
  while warmer temperatures decrease nutrient
  supply
• The highest concentration of phytoplankton forms
  at the ice edge rather then in the water column
• The phytoplankton bloom is also closely related
  to the success of cod reproduction
• Any decrease in spring blooms would adversely
  affect the entire Arctic food web
• A warmer Arctic may affect mammals who depend on
  polynyas for habitat and hunting (seals and polar
  bears)
• Warming waters may decrease nutrient supply
  through greater stratification of the water
  column
• Increased carbon could also affect the production
  of benthos thereby affecting gray whales,
  walruses and bearded seals

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Arctic Food Web
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Potential Effects on Marine Mammals

• Migrations and Movements of Marine
• Mammals Relative to the Annual Ice Cycle

• Marine mammals' migrations are tied to seasonal
  sea ice cycles so any changes in these cycles
  could affect migration patterns
• Bowhead whales, walruses, belugas, ringed seals,
  and bearded seals follow the ice edge as it
  advances and retreats therefore reductions in
  southern sea ice could push southern populations
  north
• Changes in seasonal sea ice may also affect the
  length of feeding seasons, timing of migrations,
  fecundity, and survivorship of marine mammal
  species.
• The opening of the Northwest Passage and with it
  increased human activity including pollutants,
  effects of increased ship traffic, exploration,
  industrial activities, fisheries, and associated
  noise may affect marine mammals' distribution and
  populations
• Lengthening of the open water season may also
  alter seasonal migrations

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Potential Effects on Marine Mammals

• Linkages between Changes in the
• Freshwater Budget and Marine Mammals

• Increased precipitation in the Arctic could
  adversely affect marine mammals
• Runoff from continents may affect biomass of ice
  algae, prey availability, ice formation, and
  pollutants in the Arctic.
• Increases in freshwater could disrupt the feeding
  conditions of marine fish larvae, creating a
  chain reaction in the Arctic ecosystem

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Conclusions

• Argues that increased human activity in the
  Arctic, ocean circulation, ice conditions, and
  ecosystem structure and function in the face of
  climate change are all reasons to continue and
  increase research and monitoring in the Arctic
• Managers of marine resources in the Arctic
  should be aware of present observations and
  predictions of climate change further, they
  should develop risk-averse management strategies
  that take into account possible adverse impacts
  of Arctic climate change on the ecosystem.

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10 Years Later..Arctic Sea Ice at Record Low

• 2007 has the lowest sea-ice extent since 1970s
• Opening of the Northwest Passage
• Feedback effects will make the recovery from ice
  loss difficult
• Arctic ice thickness is at 50 of what it was in
  2001
• US Geological Survey (USGS) predicts that
  two-thirds of the polar bear population could be
  lost within 50 years because of melting sea ice

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Discussion Questions

• In their conclusion Tynan and DeMaster suggest
  that environmental managers need to take a new
  approach when managing and monitoring Arctic
  mammals in the face of climate change. What kind
  of strategies would you employ in this situation?
  How can we manage in the face of so much change
  and uncertainty or can we?
• After reading the article Arctic Sea Ice at
  Record Low and comparing it to the predications
  made ten years ago in 1997 do you have a greater
  level of confidence in GCM predications?
• In Observations and Predictions of Arctic
  Climatic Change the authors argue that it may be
  premature to rule out the possibility of natural
  climate change. This was written in 1997. Do
  you think that we are now able to rule out
  natural climate change?