Bivalve Shells—Unique High-Resolution Archives of the Environmental Past - Towards an Interdisciplinary Approach in Earth System Science - page 160

environmental data prior to the instrumental era in order to improve and verify such
climate models. Therefore, climate sciences rely on climate archives such as
sediment cores and ice cores. Such archives contain

, i.e. physical,
chemical or biological properties that correlate to certain environmental parameters
and hence allow reconstructions of such parameters at the time of the formation of
the archive. The relationship between water temperature and

“ proxies ”

18 O is thought to be
the most important relationship between an environmental parameter and its proxy.
Accretionally growing hard parts of aquatic organisms (e.g., corals,

δ

sh and
squid otoliths, coralline algae, bivalve shells) are being used as climate archives

intra-annual decadal

Check for alterations:
Raman
microscopy

Correlation
or
Frequency
analysis

Seasonality:
oxygen isotopes

δ

Multi Taper Method

18 O

annual cyclicity 5-year signal

2

2

1.0

0.8

1

1

0.6

0.4

0

0

50 100 50 100

0.2

0 0

sample number sample number

0

0 0.1 0.2 0.3 0.4 0.5

Frequency (1/yr)

Fig. 1 Flow chart illustrating potential reconstruction techniques on various time-scales for
bivalve shells. Geochemical analyses, such as

18 O as a proxy for water temperatures, allow
reconstructions on an intra-annual level. A test for preservation in fossil specimens

δ

— e.g., by using

CRM should be obligatory. The shell of A. islandica can additionally be used for a frequency

analysis (e.g., Multi Taper Method) of the annual growth pattern, allowing the identi cation of
decadal variabilities, such as a 5-year quasi-periodic signal

—