Cool Cores Capture Climate Change

Goals & Objectives

To determine the effect of Earth's temperature changes, and glaciers' respective movements, on ice core sediments. -- How can one 'read' an ice core? -- What sediments are present in warm or cool climates and why are they present? -- How does one use the ANDRILL coring program? -- What does our data tell us?

ANDRILL

• ANDRILL (ANtarctic geological DRILLing) is a multinational collaboration comprised of more than 200 scientists, students, and educators from five nations (Germany, Italy, New Zealand, the United Kingdom and the United States) to recover stratigraphic records from the Antarctic margin using Cape Roberts Project (CRP) technology.

• The chief objective is to drill back in time to recover a history of paleoenvironmental changes that will guide our understanding of how fast, how large, and how frequent were glacial and interglacial changes in the Antarctica region.

• Specific science objectives of :o obtain high-resolution sediment cores that record major glacial events and

transitional periods over the past 40 million years;o determine orbital and sub-orbital glacio-climatic fluctuations that vary on 100,000,

40,000, and 20,000 year cycleso obtain a refined record of the onset and development of the East Antarctic ice sheet

(EAIS) 40 million years agoo identify how the Antarctic region responded to past events of global warmtho derive a detailed history of Antarctic Holocene environmental change at the end of

the last glaciation o test global linkages between climate changes in the Northern and Southern

hemispheres

Sediment Cores

 •Our study of past climate (paleoclimate) takes place in the Southern Ocean region, around the continent of Antarctica. •In warm climatic periods, the ice surrounding Antarctica retreats. •When this occurs the ocean is exposed to increased sunlight and air. These conditions favor an abundance of marine plant and animal life, including diatoms. Conversely, during cold periods, the ocean also cools; consequently sea ice increases and covers the ocean surface.• When sea ice covers the ocean surface, exposure to sunlight and air is reduced in the ocean below. During these times, different, and fewer, species of organisms thrive. •When ocean organisms such as diatoms die their un-decomposed silicified (carbon rich) body parts, sink to the ocean floor and become layers in the sediment. Thus, this change in life conditions is recorded in the composition of the sediment cores.

Card #1

Mudstone with clasts

Mudstone embedded with small rocks (clasts) indicates that an ice shelf covers the ocean. Glaciers pick up stones as they move across the land and become an ice shelf over the water. When the underside of the shelf melts it releases rocks and mud that settle to the sea floor. Since the ocean has been under the ice shelf away from sunlight for a long time, there will be few diatoms in this layer. Where in the picture will this layer be created?

Sediment rate = slow

Card #2

Diamictite

Diamictite is composed of coarse, angular and well-rounded clasts (rocks) of many types, embedded in a mixture of mud. It is described as poorly sorted. Diamictite is created in subglacial environments, meaning that it is deposited under the ice sheet where the ice meets the land. The clasts and sand grains may show evidence of breakage and rolling. Where in the picture will this layer be created?

Sediment rate = fast

Card #3

Diatomite

Diatomite is composed of the remains of diatoms, whose silica shells (SiO2) make up the layers of this sediment. Diatoms are single celled algae found all over the world in hundreds of species and varieties. Diatom species are temperature sensitive, so their presence is a clue to past ocean temperatures. Where diatomite is deposited, the ocean is open to the atmosphere and sunlight (not covered by sea ice) so these organisms can thrive. Where in the picture will this layer be created?

Sediment rate = slowest

Conglomerate layers are made of unsorted rocks (clasts) larger than sand, and as big as pebbles, that are cemented together in a matrix of finer grains of material. These rocks are carried along with the glacier as it advances and are generally rounded in shape. Where in the picture above would you expect to find this layer being created?

Conglomerate

Card #6

Using PSICAT

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Ice Shelf Animation

• http://andrill.org/system/files/web/images/edu/iceshelfadvanceretreat.swf

At +5 degrees, the ice shelf is completely gone. The water is exposed to sunlight and life, including diatoms, flourish. The green sediment (containing diatomite) is deposited. At -2 degrees, the ice shelf advances conglomerate is deposited and then once the ice shelf is really thick, mudstone with clasts is deposited underneath the ice shelf.

Animation CoreDiagram

Ice Core

 

How To Read an Ice Core

      Diatomite - open ocean and warm temperatures Sandstone -  sand-like rocks brought by the wind and water and cemented by pressure  Diamictite - point where ice meets land, but is not exposed to sunlight yet

 

How to Read an Ice Core

Slide 1: Ice shelf grows and contracts, as the diamictite and diatomite layers alternate. The earth undergoes periods of mild warming and cooling. Slide 2: The earth becomes warmer. The ocean is exposed to sunlight and diatoms (algae) flourish.  

Climate Change •Over the course of Earth’s history, the climate has changed dramatically, and has shifted between warm and cold phases. •For example: Antarctica and Arizona, places that were once sprawling with lush vegetation because of the warm climate, are now dry deserts•Climate change today, however, has much farther reaching effects, including: causing us to change the location of crops grown in specific areas, making the areas that people now thrive in possibly uninhabitable, and changing or eliminating current animal habitats.•By analyzing sediment cores, scientists can observe and analyze changes in Earth’s climate.

How Sediment Cores Capture Changes in Life Conditions

 •In the Southern Ocean region, around the continent of Antarctica, warm climate causes ice surrounding the continent to retreat.•As the newly uncovered ocean gets exposed to sunlight and air, marine plant and animal life, including diatoms, flourish•However, as the ocean cools during colder periods, the sea ice refreezes and covers the ocean surface that was exposed to sunlight and air, thus causing fewer organisms to survive•However, as the ocean organisms die, they sink to the ocean floor; leaving their un-decomposed silicified (carbon rich) body parts to become layers in the sediment, thus leaving a recording of a change in life conditions in the sediment.  

How Sediment Cores Capture Changes in Glacier Activity

 •Ice shelves are formed when accumulations of ice and snow over thousands of years form glaciers that flow off the land and into the ocean. •During cold periods, ice shelves advance until they are grounded on the ocean floor.•This causes them to mix the sediment layers and compact the remaining materials with their weight.•During warm periods, retreating grounded ice shelves leave marks in thick deposits of small rocks, called clasts and form smooth surfaces on which new layers start to accumulate.•In this way, sediment layers record periods of climate change.

How is the data stored in the cores decoded and analyzed?

• Specially equipped research ships use a coring apparatus to bring samples of these sediment layers to the surface as sediment cores. Once these cores are recovered, scientists are able to analyze them and uncover the story of past climates.

•  Unlike tree rings that contain a relatively short record of climate history, sediment cores—which preserve hundreds of thousands of years of Earth's history—tell a much longer story. 

• Sediment bands (seen as changes in color, texture and composition in the core) indicate climate cycles that each may span hundreds to thousands of years.

•  The record in these cores helps researchers piece together Earth's history of climate change.