Sea Level Change (PowerPoint)

					              Sea Level Change




              Geography 1050




Trout River
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Longterm
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
                    Sea Level Change

• driven by local, regional, hemispheric, & global factors
• Changes in sea level are not uniform
• Each area is affected differently
• “Global” sea level is only a theoretical concept
                    Atlantic Canada

• Effects of glacial activity
• melting of ice, adding more water to ocean
• glacio-isostatic rebound: recovery of land as ice
  weight is removed
                        NL Glaciation

•   island covered by local ice caps
•   Labrador covered by large Laurentide glacier
•   Maximum thickness 2000 m
•   Weight of ice causes glacio-isostatic depression
Glaciation
             www.bio.umass.edu/biology/conn.river/iceages.html
Glaciation & deglaciation


                            www.homepage.montana.edu/.../GLACIER%20LAB.htm
                          Deglaciation
•   Melting began 15,000 years ago
•   Complete between 9,000 and 7,000 years ago
•   Sea flooded into isostatically-depressed areas
•   135 m a.s.l. at Gull Island Rapids, Labrador
•   170 m at St. Anthony
•   58 m at Laurenceton, Bay of Exploits (photo)
•   35 m at Terra Nova National Park
                Glacio-isostatic Rebound

• Removal of weight of ice allows land to rebound

• Sea forced to recede, relative sea level drops

• Land „springs‟ back, then subsides

• Still happening around Lake Melville (1 mm per year)

• Currently, rising sea levels around island of Newfoundland
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Long term
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
                                                                         Marine Clay
                                                                         at Springdale
                                                                         indicates sea
                                                                         level was 75
                                                                         m higher than
                                                                         today 12,000
                                                                         years ago


How would you find out if this were marine clay or not? What proxy data would you use?
Dropstone indicates
iceberg rafting, in
marine clay near
Lower Churchill
project site




                      What makes this stone peculiar?
                      What proxy data could you use to
                      find out more?
                   youngest
                              Sequence of
                              “raised beaches”
                              formed as sea level
                              gradually withdrew,
                              Coastal Labrador


         younger




oldest
Raised Beach, Sandy Cove, Eastport Peninsula


                                               What kinds of proxy data
                                               would tell us this?
           Sea Level 12,000 years ago
 Old Man
 sea stack,
Trout River,
    NL
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Long term
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
            Sea-Level History in Atlantic Canada

• Higher sea levels immediately following deglaciation;

• Dropping to levels lower than present between 8,000 and
  5,000 a ago (varying from place to place);

• Currently rising (except for Lake Melville)
                    How do we know?

 for long time scales (100s or 1000s of years):
    Maps & bathymetric charts
    Archaeological sites
    14C dating
                             14C   dating

• Radiometric decay of 14C
   –   Organic deposits only
   –   Not valid for deposits younger than 1950
   –   Used for deposits up to 30,000 years old
   –   Dates expressed as “BP”
Broad Cove, Avondale




        Submerged black spruce stump
For a reliable date, the stump should be rooted in peat under
the beach gravel (so it is not a piece of driftwood).
This stump indicates sea level rise at
about 2.5 – 3 mm per year over the past 1800 years




   Ship Cove,
  Placentia Bay
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Long term
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
            Medium (intermediate) Time Scales
 Assessment over decades through human infrastructure (docks,
  moorings) and/or tide gauge records

 Airphotos and satellite imagery indicate coastal erosion, beach retreat

 Personal photographs




Topsail Beach, ca. 1910
Mooring ring was installed above high tide position ca. 1750;
today high tide rises above ring (approx to person’s helmet)




   Mooring Ring, Louisbourg, NS
Currently rising at 2 mm/a,
the wall is necessary to prevent this Beothuk site from being washe




                              Eroding archaeological site,
                              The Beaches, Bonavista Bay
Middle Cove
    Middle Cove
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Longterm
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
                            Short Term

• Humans cannot look at the sea from one year to the next
  and recognize rising levels visually
   – natural tidal changes in sea level
   – daily variations due to storms


• Recognition of relative sea level rise based on long-term
  and intermediate-term analyses.

• Tidal component must be accounted for („filtered out‟)
  before sea level rise can be recognized.
 Elevations of tidal position over time (diamonds) at Cuxhaven, Germany
• although individual levels vary, the overall trend indicates rise 1788-1995
                     0.5


                     0.4


                     0.3


                     0.2
   Water Level (m)




                     0.1


                       0


                     -0.1


                     -0.2


                     -0.3


                     -0.4


                     -0.5
                            1960   1965   1970   1975   1980      1985   1990   1995   2000   2005
                                                           Year




Port-aux-Basques: Sea level rise approx. 3.3 mm/year
                Sea Level change-net results

• Observed rates of sea level change (from all causes
  combined) in Atlantic Canada vary from 1 mm per year to
  more than 5 mm per year
   –   S. & E. Newfoundland – 3 to 5 mm per year
   –   Fundy and SW Nova Scotia – 3 mm per year
   –   Gulf of St. Lawrence coast – 2 to 3 mm per year
   –   Labrador - +1 to – 1 mm per year
                            Outline

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Longterm
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada
                   If you live on the shore …


• Sea level is rising, regardless of cause

• If your property is eroding, the cause is less important than
  is taking action

• Adaptation is required
   Adaptation Strategies

• Reinforce (armour) the coast
• Retreat and rebuild
• Rezone the coastal area




                                 Ferryland
               Bauline East
Conception Bay South

         Conception Bay
             South
                          Summary

• Patterns and processes of sea-level rise in Atlantic
  Canada
   – Glaciation, deglaciation, and isostatic rebound


• Types of evidence used to determine rates of sea-
  level rise
   – Longterm
       • Geomorphological & sendimentological evidence
       • C14 dating
   – Medium term
   – Short term


• Adaptations to sea-level rise in Atlantic Canada

				
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posted:4/9/2011
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