Quaternary Lecture 2- Stable Isotopes: the Roestta Stone of Climate Change

Question 1

What is atomic number based on?

Answer 1

Number of protons

Question 2

What do elements have a varying number of?

Answer 2

Neutrons

Question 3

How many neutrons can oxygen have?

Answer 3

7, 8, 9 or 10

Question 4

How many protons does oxygen have?

Answer 4

8

Question 5

Name 4 types of oxygen isotope.

Answer 5

15O, 16O, 17O and 18O

Question 6

What is the heaviest oxygen isotope?

Answer 6

18O

Question 7

Name two relatively stable oxygen isotopes.

Answer 7

16O and 18O

Question 8

What do variations in the ratio of 16O and 18O indicate?

Answer 8

Changing isotopic composition of ocean waters between glacials and interglacials.

Question 9

What is 16O/18O ratio in sea water controlled by?

Answer 9

Fluctuations in land-ice volume.
Down-core variations record glacial/interglacial climatic oscillations

Question 10

What does SMOW stand for?

Answer 10

Standard mean ocean water

Question 11

Discuss oxygen isotopes in glacials?

Answer 11

16O (lighter or negative delta18O) is evaporated from water more easily. Hence ocean waters are relatively enriched in 18O while ice sheet relatively enriched in 16O.

Question 12

Discuss oxygen isotopes in interglacials.

Answer 12

Melting ice sheets returned more 16O to the ocean

Question 13

What is oxygen isotope signal?

Answer 13

18O/16O ratio (delta symbol) = delta18O

Question 14

What does our record of glacier ice volume through time come from?

Answer 14

Analysis of marine microfossils in ocean floor sediments and ice cores.

Question 15

Glacial oxygen isotope record.

Answer 15

16O depletion in ocean & enrichment in ice

Question 16

Interglacial oxygen isotope record.

Answer 16

16O enrichment in ocean & depletion in ice

Question 17

Can marine sediment cored provide us with a coherent record of long term climate change?

Answer 17

Yes

Question 18

What does MIS stand for?

Answer 18

Marine isotope stages

Question 19

What do even numbers for MIS mean?

Answer 19

Cold stages

Question 20

What do odd numbers for MIS mean?

Answer 20

Warm stages

Question 21

What is an example of quaternary climato-stratigraphy?

Answer 21

Marine isotope stages

Question 22

What stage has isotopically heavier ocean water?

Answer 22

Glaciations

Question 23

What is the longest and best preserved palaeoclimate record? Why?

Answer 23

Deep sea ocean core record
- Low, regular sedimentation rate
- Negligible erosion

Question 24

Are biogenic sediments an example of proxy data?

Answer 24

Yes

Question 25

What are biogenic sediments?

Answer 25

Form from the skeletal remains of calcareous organisms (e.g. planktonic and benthic foraminifera - microfossils). - Record isotopic balance of water they inhabited - Relative abundance - Morphology/species - Preservation

Question 26

What is termination 2?

Answer 26

End of glacial periods

Question 27

Name 4 types of biogenic sediments.

Answer 27

Diatom Coccolith Ostracod Foram

Question 28

Is inorganic/terrigenous sediment and IRD a source of proxy data?

Answer 28

Yes

Question 29

What is IRD?

Answer 29

Ice rafted debris

Question 30

How is inorganic/terrigenous sediment and IRD a source of proxy data?

Answer 30

Increases during glaciations and provides a deep-sea record of ice sheet fluctuations

Question 31

What are forams useful for?

Answer 31

Reconstruction of sea surface (planktonic) and botton water (benthic) temperature and salinity.

Question 32

What can ice cores tell us about?

Answer 32

Annual layers - dating technique Volcanic eruptions- sulphur and tephra Dust (particles)- past aeolian activity and marker horizons Gas content of atmosphere- Co2, Ch4 in bubbles in the ice Temp (oxygen isotope signal)- basis for correlation with marine record

Question 33

Where is GISP2 from?

Answer 33

Greenland

Question 34

What is deuterium?

Answer 34

Deuterium is a stable isotope of hydrogen

Question 35

Is there more of less deuterium in glacier ice in interglacials?

Answer 35

More, therefore less in oceans

Question 36

What are features of cold periods?

Answer 36

increased aridity and windiness, more dust particles. Tell us about atmospheric circulation

Question 37

Where is the longest ice core?

Answer 37

Antarctica - dates around 1 million years

Question 38

How many years for Vostok core?

Answer 38

420 kyr

Question 39

How many years for EPICA core at Dome C core?

Answer 39

800 kyr

Question 40

(Quaternary) Discuss the correspondance between CO2, CH4 and temperature.

Answer 40

As gas concentration increases so does temperature.

Question 41

Discuss MIS 11.

Answer 41

A long interglacial. Analogous to the Holocene

Question 42

How many years does Greenland ice sheet stretch back?

Answer 42

120,000 years

Question 43

What is Operation Ice Bridge?

Answer 43

Scientists using ice-penetrating radar data collected by NASA’s Operation IceBridge and earlier airborne campaigns have built the first-ever comprehensive map of layers deep inside the Greenland Ice Sheet

Question 44

What are 'sub-Milankovitch' events?

Answer 44

High frequency climate oscillations – sub-milankovitch events = interstadials/stadials within glacial/interglacial cycles

Question 45

Where are sub-Milankovitch events prevalent?

Answer 45

Greenland ice core records

Question 46

Discuss the cyclicity of sub-milankovitch records.

Answer 46

Some appear to have a cyclity during the last cold stage (80–20ka BP).

Question 47

Discuss sub-Milankovitch events.

Answer 47

Temperature changes of 7˚C between warm & cold stages. Abrupt start; more gradual decline (saw-tooth pattern)

Question 48

Name the three types of sub-Milankovitch events.

Answer 48

Heinrich events D-O events Bond Cycles

Question 49

Discuss Heinrich events

Answer 49

Marked by layers rich in ice-rafted debris (IRD) in marine sediment cores, which record massive iceberg discharges (binge/purge cycles of ice sheets; MacAyeal, 1992) with a ~cyclic occurrence. H’ Events tend to coincide with the end (cold phase) of Bond Cycles

Question 50

Discuss D-O events

Answer 50

Rapid climate fluctuations during the last cold stage; ~20 in number, with a periodicity between 1000-2000 yrs. First discovered by Willi Dansgaard in the 1970s and written off as ‘noise’

Question 51

Discuss bond cycles.

Answer 51

longer term cooling cycles 1,000-15,000 years long during the last cold stage - long cooling cycles & abrupt warming

Question 52

Name 5 things which can influence sub-Milankovitch changes.

Answer 52

Ocean circulation Atmospheric circualtion Ice/fresh water flux to the ocean Ice sheet growth Ice sheet collapse

Question 53

Discuss thermohaline circulation in relation to ice sheets.

Answer 53

The strength of the Thermohaline circulation is sensitive to freshwater input (reduces density so harder to sink ; it can slow down/stop – hence patterns of cooling/warming in N Atlantic region are very sensitive to ice sheet growth and decay as freshwater flux can effect North Atlantic Deep Water (NADW) overturn

Question 54

What are temperature and salinity-driven currents initiated by?

Answer 54

Cooling of surface water and increasing of its density Addition or removal of freshwater (e.g. iceberg armadas or lake bursts)

Question 55

Discuss IRD (heinrich layers) and ice sheet binge/purge cycles.

Answer 55

Six layers of Ice Rafted Debris (IRD) detected in North Atlantic sediment cores –’Heinrich Layers’ from the Laurentide ice sheet Heinrich Layers (H1-H6) deposited ~70-14 ka BP. Frequency 7-10 ka yrs We now know that the British and Fennoscandian ice sheets also delivered IRD to the N Atlantic.

Question 56

What did MacAyeal suggest in terms of ice sheet cyclical growth?

Answer 56

ice sheet cyclical growth and decay was important for iceberg and freshwater flux to the ocean ……which subsequently influences thermohaline circulation