Sea Level Change
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Transcript of Sea Level Change
![Page 1: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/1.jpg)
Sea Level Change
Geography 1050
Trout River
![Page 2: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/2.jpg)
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
![Page 3: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/3.jpg)
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
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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
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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
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Glaciation
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Glaciation & deglaciation
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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
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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
![Page 10: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/10.jpg)
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
![Page 11: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/11.jpg)
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?
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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?
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Sequence of “raised beaches” formed as sea level gradually withdrew,
Coastal Labrador
oldest
younger
youngest
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Raised Beach, Sandy Cove, Eastport Peninsula
Sea Level 12,000 years ago
What kinds of proxy data would tell us this?
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Old Man
sea stack,
Trout River, NL
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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
![Page 17: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/17.jpg)
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)
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How do we know?
for long time scales (100s or 1000s of years): Maps & bathymetric charts Archaeological sites 14C dating
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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”
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Broad Cove, Avondale
Submerged black spruce stump
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Ship Cove,
Placentia Bay
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
![Page 22: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/22.jpg)
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
![Page 23: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/23.jpg)
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
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Mooring Ring, Louisbourg, NS
Mooring ring was installed above high tide position ca. 1750;
today high tide rises above ring (approx to person’s helmet)
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Eroding archaeological site,
The Beaches, Bonavista Bay
Currently rising at 2 mm/a, the wall is necessary to prevent this Beothuk site from being washed away
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Middle Cove
Middle Cove
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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
![Page 28: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/28.jpg)
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.
![Page 29: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/29.jpg)
Elevations of tidal position over time (diamonds) at Cuxhaven, Germany
• although individual levels vary, the overall trend indicates rise 1788-1995
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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
Year
Water Level (m)
Port-aux-Basques: Sea level rise approx. 3.3 mm/year
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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
![Page 32: Sea Level Change](https://reader036.fdocuments.us/reader036/viewer/2022062517/5681351b550346895d9c7459/html5/thumbnails/32.jpg)
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
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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
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Adaptation Strategies
• Reinforce (armour) the coast
• Retreat and rebuild
• Rezone the coastal area
FerrylandBauline East
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Conception Bay South
Conception Bay South
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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