time traveling with fairbanks weather sci-05, fall semester 2015 week 4: time scales of centuries to...

Time Traveling with Fairbanks Weather

SCI-05, Fall Semester 2015Week 4: Time scales of Centuries to Millenia

Instructor/Destructor Eric Stevenseric@gina.alaska.edu

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Previously on OLLI SCI-05…

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Hurricane JoaquinAs 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/blog/wp-content/uploads/2015/09/1000x1600_AGOES13_B3_SC_FLOODINGWV_animated_2015274_004500_180_2015278_144500_180_WVCOLOR35.gif https://www.facebook.com/NWS/videos/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”

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Image from http://cimss.ssec.wisc.edu/goes/blog/archives/19750

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

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Meet Our Protagonist: The Sun

The Time Scale out to One Year

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Meet Our Protagonist: The Sun

The Time Scale Centuries to Millenia

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Meet Our Protagonist: The Sun

Fairbanks Through The Holocene

Rick ThomanNational 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?10/09/201514

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 Maximum10/09/201516

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• 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

Source: Marcott et. al. 2013

December

June

Annual

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Solar Irradiance in the Holocene

Variation around 1986 mean value of 1364.6 Wm-2

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 from Marcott et. al. 2013 10/09/201531

Latitudinal Variation in Holocene

Temperatures

Based on Marcott et. al. 2013 10/09/201532

Holocene Summary

• Early Holocene (11.7k to 7k BP)• Obliquity > now (Arctic Circle south of Dalton Hwy

Yukon River Crossing)• Perihelion in summer

• More heating summer

• Ice sheets present but decrease rapidly

• Mid-Holocene (7-3.5k BP)• 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) 10/09/201533

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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