The Quaternary Period

2.58 Ma to present

The Quaternary Period

The Quaternary Period

What are cyclic (repeating) and secular (long-term) changes?

Zooming out over the Plio-Pleistocene

Orbital cycles

Obliquity

41 kyr period

Axial Precession

∼26 kyr period

Eccentricity

∼100 kyr period

Solar forcing at 65°N on the summer solstice

Can orbital cycles account for increasing amplitude of climate change?

No secular change. So what is changing? Climate sensitivity via ↓ CO₂

Glacial-interglacial pacing

Data: Lisiecki+Raymo 2004

1. Measure the distance between adjacent extrema (peak-peak, trough-trough)…
   • Before 1500 ka
   • After 500 ka
2. Use the x-axis ticks to convert your measurements to time.
3. Interpret your results. What is going on?

Mid-Pleistocene Transition

Between 1200 and 700 ka shift from ∼41 kyr cycle to ∼100 kyr cycle

Internal climate system forcings maintain glacial conditions through several cycles until it hits a tipping point (threshold)

Zine Project

What is a zine (zeen)?

• DIY, low tech, inexpensively produced
• Often published and distributed by authors/artists themselves
• Anti-commercial, often rebellious/anti-establishment
• About a wide range of subjects: poetry, politics, music, scifi, fandom …
• Accessible to everyone — free or cheap and readily available

Pamphleteering could be considered an early form of zinemaking

Zines started in the early/mid 20th century as fanzines

The Reign of the Superman

January 1933 by Jerry Siegel and Joe Shuster

The Comet

Chicago in 1930 by Raymond Arthur Palmer and the Science Correspondence Club

Zines exploded with Punk in the 1970s

Activist zines took off with feminist zines and continue with other activist movements

Folks make zines about EVERYTHING from humor to politics to science!

Folding a 6-page fold-up zine

Assignment

Design and create a 6-page zine describing an aspect of Earth's climate system, climate history, and/or climate science techniques.

Create an accessible, digestible mini-publication to breakdown and explain a complex issue to a non-scientist.

Due: 5pm | December 6

Format

• Front cover — title and author name(s)
• Interior pages (6) —scientific content in text, images, and diagrams
• Back cover — references for all images and literature
• (Optional) a large image, diagram, or map within folds

Content

You have a lot of flexibility for your zine topic, but I expect you to engage with it at a depth and level appropriate to this class …

…If you have are unsure if your topic will satisfy the requirements of the project, I am more than happy to discuss during drop-in hours or provide feedback on a topic proposal

References

Your zine must incorporate at least three (≥3) primary resources. These must be reputable sources that adhere to the publishing practices of their fields (e.g. peer-review for scientific articles).

Abbreviated reference style

Collaboration

You may work with a partner if you choose.

If you work with a partner, please include a brief “Author Contributions” section either on the back cover of your zine or as a supplemental document.

Proposal

A short (<150 word) description of your zine idea. I will make every effort to provide feedback on your proposal within 72 hours.

Due: 11:59 pm 20 Nov

Many ways to make a zine!

Collage with cut/torn paper and found images

1. Analog
2. InDesign (Adobe)
3. Inkscape
4. LaTeX (Overleaf)
5. … something else?!

Some rad zine resources for help/inspiration

Art Cart in Coates Library

• San Antonio Public Library
• Quarantine Public Library
• Small Science Collective
• How to Make a Zine
• Scattered Zine @ Trinity

Climate change of the last glacial period

Millenial-scale climate change over Greenland

Dansgaard-Oeschger (DO) Events

North Atlantic sediment cores

Ice-rafted debris (IRD) in North Atlantic sediment cores

“IRD belt”

IUP

Ice-rafted debris

… carried far out into the deep ocean by a large iceberg → ice shelf origins

M. Mieneck-Vautravers

Kuijpers+

Heinrich Events

Heinrich events

Few icebergs

Coarse, "lithic" sediment deposited beneath ice shelf.

Many icebergs

Carry IRD into deep ocean. Each layer corresponds to a calving event.

Ice streams of the Laurentide Ice Sheet (LIS)

Ice streams of the Laurentide Ice Sheet (LIS)

Sites of major ice streams are deep bays and lakes today (an interglacial)

Ice streams of the Laurentide Ice Sheet (LIS)

Hudson Strait Ice Stream

• Largest ice stream of LIS
• Located in Labrador Sea → North Atlantic
• Overlays carbonate rock & carbonate IRD most common in Heinrich event layers

The source!

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Margold+ 2015

Activating an ice stream

Requires:

1. Intermittent ice stream activation/acceleration
2. Dormant for 5–7 kyr

How can we speed up ice flow?

Activating a large ice stream

Option 1: enlarge/expel

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"Internal" ice sheet forcing

Option 2: subsurface ocean warmth

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"External" climate forcing

Overall consensus: climate forcing (#2)

(You don't need to know diagram)

• The variability in Heinrich event timing (5–7+ kyr) supports an "external" influence
• Other maritime ice streams also accelerate during HEs
• BUT, ice requires time to thicken → sensitive to climate.

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Edwards+ 2022

The DO-HE Process

DO interstadial

DO stadial

Heinrich stadial

Heinrich stadial → interstadial

Escape from the North Atlantic!

Antarctic Isotope Maxima (AIMs)

Antarctic ice δ¹⁸O rises during stadials, when Greenland δ¹⁸O is low.

Polar See-saw

Brought to you by Thermohaline Circulation

Wikipedia: Thermohaline circulation

Stadials

• cooler/cooling N. Atlantic
• more meltwater/sea ice
• weaker Gulf stream
• warmer/warming S. Ocean

Hulu Cave, China

Where does that O come from???

Hulu cave speleothems

Changes in East Asian Monsoon

Siku Events — IRD in North Pacfic

Siku Events — IRD in North Pacfic

Walczak+ 2020

H#	Heinrich events
S#	Siku events
···	Radiocarbon age of N Pacific water

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What is going on here?

Putting it all together

WHAT IS GOING ON HERE?

The Last Glacial Termination:
All good things come to an end

The Northern (Atlantic) Perspective

Last Glacial Maximum (LGM): 20–26 ka

The Bølling-Allerod (B-A) Interstadial

~15–13 ka: Final interstadial after prolonged, gradually warming stadial

Earth system still acting like it's a glacial period

The Younger Dryas

Mountain avens (Dryas octopetala) thrives in cold, alpine-Arctic climates

Wikimedia

↑↑ Dryas pollen in pond/lake cores 12.9–11.7 ka → cooling

Global Pollen Project

The Younger Dryas

Last Glacial Maximum ice margin

Context

• Ice sheet margin retreat
• B-A interstadial warmth
• Global sea levels rose by 40 m during B-A

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←How is this map changing?

The Younger Dryas

Tarasov & Peltier, 206

Ice/moraine-dammed lakes

Meltwater drainage

Freshwater → N Atlantic

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Outburst flood → rapid N Atl freshening → slows THC

After the Younger Dryas

Inter-hemispheric perspective

Inter-hemispheric perspective

The Younger Dryas — globally

Reflections: ending a glacial

LGM: 20–26 ka

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• Orbital forcing 70–0 ka
• Eccentricity
• Obliquity
• Precession
• Insolation