Glacial Change in Antarctica: How we know and what we ... · Glacial Change in Antarctica: How we...

Glacial Change in Antarctica:How we know and what we might

do about it

Julia Wellner

Earth & Atmospheric Sciences

University of Houston

UH Law School October 16th, 2019

Plan

• Antarctic basics

• Who am I and what do I do?

• Thwaites Glacier– How it’s changing

– How do we know

• Geo-Engineering of ice sheets

Sea level would rise about 70 m

– many of the world's large population centers would be flooded

What would happen if all glaciers melted?

Where is all that ice?

~65 m is in

Antarctica

~65 m is in

Antarctica

Where is all that ice?

Antarctica: Highest Continent

Antarctic Temperature Change

Mass balance is what counts, not temperature anyway

Rignot et al., 2008

Measurements

from:

•SAR

Interferometry

•GRACE

Ice Behavior is Controlled by Water (2 of 3 ways in Antarctica)

11

The WAIS, and Peninsula Ice Cap, are:

•Grounded below sea level

•On a Foredeepened shelf

•Many areas have ice shelves

Marine-based Ice

Plan




– How do we know


Quickly: What do I do?

R/V Mishipeshu University of Houston

15Different Scale

What do we do?

16

What do we do? Core on sunny days

17Photo by Y. Muñoz (2010)

What do we do? Core on cold days

18

Photo by K. Gavahan (2012)

What do we do? Core Repository

19

What do we do? Seismic

20

(2005)

What do we do? Multibeam Swath Bathymetry

21

(2002)

What do we do? Collaborate with ocean and bio teams

22CTD Photo by Y. Muñoz (2010)

Kimberly Mead

Yuribia Muñoz with Amy Leventer

What do we do? GPS (rebound)

23Photos by Y. Muñoz (2010)

What do we do? Go Ashore in Small Boats (cheaper than helo)

24

(2012)

(1998)

What do we do? Date Sediments

25

Gamma-ray spectrometry to measure 210Pb, 137Cs, other

What do we do? Sediment size, shape, texture

26

Small conchoidalfractures

Dish-shaped concavitity

Geology, but highly interdisciplinaryW

elln

er, e

t al

., 2

01

9

Plan




– How do we know


• Antarctica may contribute up to 1meter to global mean sea level (GMSL) in this century*.

• More data is required from Thwaites Glacier to improve predictive climate models.

30* Based on DeConto and Pollard, 2016

Future of the West Antarctic Ice Sheet

Modeled Scenarios of Antarctic Contribution to GMSL

EAIS

WAISAmundsen

Sea

Ross Sea

Weddell Sea

WAIS: West Antarctic Ice SheetEAIS: East Antarctic Ice Sheet

1000 km

31* Based on DeConto and Pollard, 2016

Future of the West Antarctic Ice Sheet

Ross Sea

Weddell Sea

Amundsen Sea

• Antarctica may contribute up to 1meter to global mean sea level (GMSL) in this century*.

• More data is required from Thwaites Glacier to improve predictive climate models.

Modeled Scenarios of Antarctic Contribution to GMSL

EAIS

WAIS: West Antarctic Ice SheetEAIS: East Antarctic Ice Sheet

Thwaites Glacier Catchment

1000 km

Marine Ice Sheets, Stability, Instability, and Sediments

Introduction Ice Extent Dating Amundsen Sea

Thwaites Glacier

Amundsen Sea

https://thwaitesglacieroffshoreresearch.org/


THwaites Offshore Research

mailto:https://thwaitesglacieroffshoreresearch.org/

Stability is dependent on…•Atmospheric conditions

•Oceanographic changes

•Bed topography

Warm, saline Circumpolar Deep Water


Need to reconstruct glacier position using sedimentary facies and age modeling.

Warm, saline Circumpolar Deep Water

When did Thwaites lift off pinning points?


Glacial Marine Depositional Model

Model adapted from Kirshner et al., 2012; Hillenbrand et al., 2013; Smith et al., 2017

Coarse-grained,Poorly sorted ornormal grading

Grounding ZoneProximal

1

Seasonally Open Marine

Diatomaceous, silty clayLarger clasts (ice rafting)

3

Sub-Ice Shelf

Laminated silty clay

2

12 3


2019 Field Season in the Amundsen Sea

Research Vessel/Ice BreakerNathaniel B. Palmer

Map of ship track, ice imagery, & preexisting bathymetry near Thwaites Glacier.

Ship Track

Thwaites Ice Shelf

Amundsen Sea

Thwaites

Ph

oto

: Jam

es K

irkh

am


Rugged Seafloor Near Thwaites Glacier

Cored on two bathymetric highs that are possible pinning points in the past.

Amundsen Sea

ThwaitesNew bathymetry data and core sites around Thwaites Glacier

Thwaites Ice Shelf

Modern

Pinning Point


Preliminary Interpretation - KC04

Clay laminations and sand lenses with sparse gravel

Sandy mud with some gravel

Pebbly sandy mud with cobbles, high shear strength at base

Sandy mud, no gravel

km

Amundsen Sea

KC04


Unpinning of Thwaites Ice Shelf

12 3

km

Amundsen Sea

KC04

Grounded Ice Extent

Proximal to grounded ice

Subglacial till?1



1

1

12 3

Gradually less proximal

km

Amundsen Sea

KC04

Grounded Ice Extent


Subglacial till?



1

Transitional facies

km

Amundsen Sea

KC04

Grounded Ice Extent


Subglacial till?


2

12 3

1



1

3

12 3

Seasonally open marine

Transitional facies

km

Amundsen Sea

KC04

Modern Ice Shelf Margin


Subglacial till?


2

1


Ongoing Work

Dates imminent

Back to field in January

Thwaites Ice Shelf

Paleo Pinning Point #2

Modern Pinning Point

Paleo Pinning Point #1


Plan• Antarctic basics


• Thwaites Glacier

– How it’s changing

– How do we know


Control water flow: Can’t even do that in warm waters

Build a pinning point: What about surface melt?

Make snow: Never ending battle

Manique Talia-Murray

Thanks, questions?

Glacial Change in Antarctica: How we know and what we ... · Glacial Change in Antarctica: How we...

Documents

Transcript of Glacial Change in Antarctica: How we know and what we ... · Glacial Change in Antarctica: How we...