Time Traveling with Fairbanks
Weather
SCI-05, Fall Semester 2015
Week 4: Time scales of Centuries to Millenia
Instructor/Destructor Eric Stevens
eric@gina.alaska.edu
10/09/2015
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Previously on OLLI SCI-05…
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Hurricane Joaquin
As seen from NASA’s Aqua satellite,
the MODIS instrument
• http://aqua.nasa.gov/
• http://modis.gsfc.nasa.gov/
• http://cimss.ssec.wisc.edu/goes
/blog/archives/19662
New Imagery!
http://cimss.ssec.wisc.edu/goes/blo
g/wpcontent/uploads/2015/09/1000x16
00_AGOES13_B3_SC_FLOODINGWV
_animated_2015274_004500_180_
2015278_144500_180_WVCOLOR3
5.gif
https://www.facebook.com/NWS/vi
deos/10154326165029041/
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Not to Be Outdone, We Get Oho
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Not to Be Outdone, We Get Oho
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Satellite Loop of
“Total Precipitable Water”
Image from http://cimss.ssec.wisc.edu/goes/blog/archives/19750
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Today’s Phenomena
• Deep Time
• Mechanisms that influence weather and
climate in Fairbanks on time scales of
centuries to millenia
• Special Guest lecturer Rick Thoman of the
National Weather Service
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The Time Scale of one Day
Meet Our Protagonist: The Sun
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The Time Scale out to One Year
Meet Our Protagonist: The Sun
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The Time Scale Centuries to Millenia
Meet Our Protagonist: The Sun
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Fairbanks Through
The Holocene
Rick Thoman
National Weather Service
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Today
• What’s the Holocene?
• What is climate?
• Reconstructing past climates
• Climate drivers at 100 to 1000 year time scales
• Fairbanks through the Holocene
• The past: a guide to the future?
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Events you might
remember
• April 3, 979BP: Extremely warm spring: early
break-up of Tanana R. at Nenana
• July 18-19, 2822BP: 3 to 8” rain causes
widespread flooding
• December 20-Jan22, 6363BP: temperatures
continuously remains 45 below or lower
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Holocene
• Informally, epoch since the end of the ice age
• Began July 22, 11,700BP, about tea time
(approximately)
• People have lived in Interior Alaska the entire
Holocene
Continents at the Last Glacier Maximum
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Geographic Features of
the Holocene
• Pacific Ocean connection to the Arctic Ocean
(Bering Strait breached 11-12k BP)
• Reduction in land area (continental shelves
submerged)
• Extremely important for Interior Alaska
• Decreased Continental Ice Sheets
• European Ice Sheet gone by 9k BP
• Cordilleran Ice Sheet gone by 7k BP
• Laurentide Ice sheet gone by 6k BP
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What’s Climate?
• “Climate’s what you expect, weather’s what
you get” attributed to Mark Twain
• Climate is what’s in your closet. Weather is
what you where today
Climate is nothing more or less than
the statistics of weather
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This is Climate
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The Full Climate System
• Long term climate system
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Earth and Sun (Solar Heating, Albedo)
Atmosphere
Hydrosphere (Oceans, Fresh water)
Cryosphere (Sea Ice and Glaciers)
Biosphere
Chaotic, non-linear system
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Reconstructing Holocene
Climates
• Multi-evidential lines
• Ice cores and gas isotopes
• Biotic Evidence
• Tree rings, pollen, corrals
• Permafrost
• Glacier variability
• Temporal resolution century or longer
• Only generalized climate reconstructable
• Often season specific
• Numerical climate modeling can provide insight
Always a risk of overgeneralizing local or
regional evidence
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Century to Millennial Scale
Climate Drivers
• Variations in Earth’s Orbital and Rotational Characteristics
• Greenhouse Gases (Water Vapor, Carbon Dioxide, Methane)
• Northern Hemisphere land coverage
• Glaciers
• Sea Levels
• Solar Irradiance Variations
• Deep Ocean Circulations
• Volcanoes (special circumstances)
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Orbital and Rotational
Variations
• Milankovitch (1941)
• Orbital Eccentricity (variations in the shape of
the earth's orbit around the sun.)
• Obliquity (tilt of the Earth’s axis)
• Precession (timing of closest approach to the
sun)
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Primary Earth Rotation and
Orbital Variations
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Precession of the
Equinoxes
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Changes in Solar Heating
from Earth Variations
December
June
Annual
Source: Marcott et. al. 2013
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Solar Irradiance in the
Holocene
Variation around 1986 mean value of 1364.6 Wm-2
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Source: Steinhilber et. al. 2009
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Holocene Carbon Dioxide Levels
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Thermohaline Circulation
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Thermohaline Circulation
• Disruption of ocean circulation (especially
North Atlantic) has potential to impact climate
by reducing poleward heat transport
• Unclear how deep ocean circulation worked
pre-Holocene or to what extent disrupted by
continental ice sheet melting
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Global Holocene
Temperatures
Redrawn from31 Marcott et. al. 2013
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Latitudinal Variation in
Holocene Temperatures
Based on Marcott
et. al. 2013
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Holocene Summary
• Early Holocene (11.7k to 7k BP)
• Obliquity > now (Arctic Circle south of Dalton Hwy Yukon River
Crossing)
• Perihelion in summer
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More heating summer
Ice sheets present but decrease rapidly
• Mid-Holocene (7-3.5k BP)
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Obliquity > now (Arctic Circle south of Finger Mtn)
Perihelion in spring
Minimum in Alaska Glacial coverage
• Now (since 3.5K)
• Arctic Circle continuing to move northward
• Perihelion in winter
• Multiple glacial advances/retreats (large advances coastal
Alaska)
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Interior Alaska Vegetation
During the Holocene
• Very early Holocene…major expansion of birch with scattered
balsam poplar. A shrub parkland, but appears not to have
involved a lot of aspen. Probably a transitional stage
• 10k to ~7k BP, Hardwoods present, but continuous forest
canopies may have been less common than today White spruce
less abundant, and black spruce was essentially absent. Largely
because of the sparser spruce cover, fires were relatively
infrequent.
• About ~7k BP: Cooler, and there was a greater effective annual
moisture regime (e.g. lake levels rose in restricted circulation
basins). Black spruce spread across Interior Alaska, and the forest
cover and fire regime we have today began.
Source: Glenn Juday, pc
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Putting it all together:
Fairbanks’s Holocene Climate
• Dramatic warming and wetting start of the
Holocene
• 10k-7k BP: summers warmer but moist, winters
somewhat colder
• 7k-3k BP: summers cooler than previously but
possibly longer: winters similar to cooler
• 3k BP-present: similar to 20th century. Regional
reflection of “medieval warm period” and “little
ice age” unclear
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The Future Millennia
• What we know
• Perihelion will move toward occurring in the
spring (5k) and then summer (10k)
• Orbital eccentricity will decrease (30k)
• Obliquity will decrease (10k)
• CO2 much higher than Holocene (at least 250
years)
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Summary
• Large scale: Evolution in Holocene climate are
strongly tied to changes in Earth-Sun
variations
• Climate as been stable — relative to the
Pleistocene — but enough to change
dominant vegetation
• Just like investing, past performance may not
be a guide to the future returns.
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