Transcript 261 Lect 2 Alaska Geology & Climate 24JAN2011

Alaska Map
Alaska Geography Facts I
663,268 sq miles, including territorial waters
21% of the area of the entire lower 48.
Bounded by:
Gulf of Alaska
Bering Sea
Chukchi Sea
Beaufort Sea (Arctic Ocean)
Alaska Geography Facts II
Width: West - East 808 miles
Length: North - South 1,479 miles
Controlled by Federal Gov’t: 65% total area
Shoreline: 34,000 miles
Two Time Zones: Alaskan Aleutian
Population (2006) 670,053
Alaska Geography Facts III
Coastline Alaska:
33,904 miles
Coastline Lower 48: 54,729 miles
Alaska has 62% total Tidal Coastline of US
Area of Continental Shelf in Alaska is huge
Most fish are caught near shore and on the
continental shelf
Geology of Alaska I
Two Major Tectonic Plates
North American Plate & Pacific Plate
Understanding Plate Interactions Important
Transform Boundary - sliding along
Divergent Boundary - mid ocean ridge
Convergent Boundary - subduction zone
Geology of Alaska II
North American Plate: NA Craton is the Core
NA Craton Rock: North/East corner of Alaska
Remainder of Alaska is accreted terrain, rocks from
further south that have been sequentially
transported to Alaska by Plate Tectonics. Many
different terrains.
Continental Shelf is part of the Continental Plate
Kula Plate - Oceanic plate subducted under NA but a
last fragment accreted to shallow Bering Sea shelf.
Alaskan Geological Map
Plate Tectonics
Oceanic versus Continental Plates
Ocean Spreading Centers
Mid-Oceanic Ridge
Volcanic Activity - Black Smokers
Seamounts
Continental Plates Override Oceanic Plates
Oceanic Plates dive into Subduction Zones
Alaska Marine Map
Beaufort Sea
Chukchi Sea
Bering Sea
Gulf of Alaska
Alaskan Marine Regions
Southeast Alaska Inland Waters
Gulf of Alaska Coast
Western Gulf of Alaska
Alaska Peninsula
Bering Sea
Yukon Kuskokwim Delta
Aleutian Islands
Seward Peninsula Norton Sound
Chukchi Sea
Beaufort Sea
Yukon River Delta
Freshwater Alaska
More than 3 million lakes in Alaska
Marshland & Wetland Permafrost Account for
188,320 sq mi of territory
Alaska has 12,000 rivers, many with salmon runs
51 Tidewater Glaciers
Many Glaciers feed Rivers, Marshes and Lakes
USDA Alaska Freshwater Districts Map
Alaska Annual Rainfall Map
Geology & Fishing
What does this have to do with fishing?
1. Nutrients eroded from rock feed food web
2. Ocean spreading centers & nutrients
3. Volcanism from subducted plates & nutrients
4. Freshwater Habitat for anadromous fish
5. Seamounts bring huge diversity
6. Fish Predators live on land
Alaskan Climate
Latitude: 51° 20’ North to 71° 50’ North
Longitude: 130° West to 172° East
Record High Temp: 100°F Fort Yukon
Record Low Temp: -80°F Prospect Creek
Sea Ice: Cook Inlet, Bering, Chukchi and
Beaufort Seas.
Alaska’s 35 Different Growing Zones
Global Warming
What will be the effects of Global Warming?
1. Warmer water species will migrate north
2. Colder water species will migrate north
3. Ocean currents will change
4. Potentially profound effects on species
distribution and abundance
Regional Climate Change
El Niño & La Niña:
Short term climatic fluctuations
1997 El Niño
1. Weird milky algal bloom in Bering Sea
visible from space.
2. Implicated in protist infestations of many
commercial species.
Pacific Decadal Oscillation
PDO is a pattern of Pacific climate variability
that shifts phases on at least inter-decadal
time scale, usually about 20 to 30 years
PDO provokes a faunal regime shift, where
the animals found most abundantly change
in cold to warm and warm to cold shifts.
Cold - crab, shrimp, herring, capelin
Warm - cod, pollock, salmon
Pacific Decadal Oscillation
Cold Phase
Warm Phase
PDO Index
The PDO Index is calculated by spatially
averaging monthly sea surface temperature
of the Pacific Ocean north of 20°N. The
global average anomaly is then subtracted
to account for global warming. Only
October to March values are used because
year-to-year fluctuations are most apparent
during the winter months.
PDO Index
Alaska Ocean Warming
Warming of the Gulf of Alaska ~1975
Geology & Fisheries
Nutrient Input (Limiting Minerals)
1. Deep-Water Upwelling
2. Loess - Wind Borne Dust
3. Volcanic Ash
4. Tidewater Glaciers
5. Suspended Riverine Sediments
6. Nutrients Released at Ice Edge
Algae Require Mineral Micro-Nutrients
Temperature, Light and Nutrients
Control Algal Blooms
1. Growth of some algal species limited by nutrient
availability (eg. Silica & Iron .
2. With appropriate nutrients, temperature and light
regulate bloom growth rates.
3. Long days in late spring can promote huge blooms.
4. Single cell algae are the base of marine food
chains.
Loess - Wind Blown Sediment
Suspended Riverine Sediments
Tidewater Glacier Alaska
Wind Blown Volcanic Ash I
Wind Blown Volcanic Ash II
Alaskan Volcanoes
Sediment & Algal Bloom Gulf of Alaska
Alaska Algal Bloom I
Alaska Algal Bloom II
Alaska Algal Bloom III
Baltic Sea Algal Bloom
Arabian Sea Algal Bloom
Black Sea Algal Bloom
Atlantic Ireland Algal Bloom
Barents Sea Algal Bloom