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Palaeogeography, Palaeoclimatology, Palaeoecology 302 (2011) 1–9
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Palaeogeography, Palaeoclimatology, Palaeoecology
j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p a l a e o
Reconstructing mid- to high-latitude marine climate and ocean variability using
bivalves, coralline algae, and marine sediment cores from the Northern Hemisphere
Alan D. Wanamaker Jr. a,⁎, Steffen Hetzinger b,1, Jochen Halfar b
a
b
Department of Geological and Atmospheric Sciences, Iowa State University, Ames, IA 50011-3212, USA
CPS-Department, University of Toronto Mississauga, 3359 Mississauga Rd. N, Mississauga, ON, Canada L5L 1C6
a r t i c l e
i n f o
Article history:
Received 28 August 2010
Received in revised form 23 December 2010
Accepted 29 December 2010
Available online 13 January 2011
Keywords:
Marine climate change
Bivalves
Coralline algae
Sediment records
High-resolution proxy records
a b s t r a c t
Quantifying the role and contribution of the world's oceans in past, present, and future global change is an
essential goal in climate, paleoclimate and environmental studies. Although the global oceans interact and
influence climate greatly, the marine environment is substantially under-represented in key climate
assessment reports, especially during the last millennium (IPCC, 2007; see Palaeoclimate chapter: 6.6—The
last 2000 years). The under-representation of marine records in key climate documents likely results from the
often imprecise chronologies associated with many marine-based archives, which greatly hinders singular
climate comparisons (lag/lead phasing relationships) with well-dated, and/or annually-resolved archives.
However, several marine archive records have excellent chronological constraint. In particular, many marine
bivalve taxa and coralline algae have annual increments that form within their carbonate framework, that can
be used to establish an absolutely-dated chronology, via cross-dating techniques, from the marine
environment. Additionally, in some cases, where sedimentation rates are high, and alternative chronological
dating methods exist (e.g., tephrochronology) other than radiocarbon measurements (often greater than
± 40 years uncertainty), sediment archives can provide continuous, sub-decadal records of environmental
change for centuries to millennia. This brief introductory article and accompanying special issue will focus on
the utilization of bivalves, coralline algae, and high-resolution marine sediment cores in paleoclimate and
environmental studies within the most recent millennium with a focus on the Northern Hemisphere.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction and rationale
There is a critical need in climate studies to characterize the past
behavior of the climate system on multiple time scales from a variety of
geographic locations. Spatially and temporally diverse proxy-climate
records can be used to elicit detailed information regarding the various
factors that influence climate (Mann et al., 2009; Mayewski et al., 2004).
Knowledge of those factors that may have been likely to initiate rapid
climate change events, especially within the last millennium, is critically
needed (IPCC, 2007; 4th Assessment Report, Intergovernmental Panel on
Climate Change). The scarcity of such climate records, especially from the
extratropical oceans, represents a serious knowledge gap in climate
studies, especially when considering that rapid climate change transitions
are likely to have substantial impact on human populations and create
severe societal challenges in the future. Further, by providing a framework
of past marine climate variability, climate scientists and climate modelers
will be better able to predict the impacts of anthropogenic activity
(namely increased CO2 emissions) on the modern and future climate
⁎ Corresponding author. Tel.: +1 515 294 5142.
E-mail address: [email protected] (A.D. Wanamaker).
1
Now at: Leibniz Institute of Marine Sciences (IFM-GEOMAR), Wischhofstr. 1-3,
24148 Kiel, Germany.
0031-0182/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.palaeo.2010.12.024
system by utilizing high-quality proxy climate data in climate model
simulations and comparisons (see McCarroll, 2010).
Given the spatial and temporal limitations of high-resolution
observational records of past ocean conditions, reconstructions of
marine environmental parameters have to rely on archival information, often derived from long-lived marine biota or sediment. While
high-resolution proxy-based marine paleoclimate studies have
traditionally concentrated on the tropics, numerous proxy time series
have been generated from mid- and high-latitude oceans during the
recent decades. This is important because the extratropical oceans,
particularly the North Atlantic, play an essential role in regulating the
global climate system via deepwater formation and carbon storage.
In a recent review of paleoclimate archives, Jones et al. (2009a)
discuss tree rings, corals, ice cores and historical information as
making up the bulk of high-resolution climate proxy information.
While speleothems, lacustrine and varved sediments are reviewed as
additional high-resolution archives, impressive recent advances in
bivalve sclerochronology and to a lesser extent coralline algal
sclerochronology are largely neglected. The latter archives, however,
are able to fill the gap left by the spatially restricted occurrence of
reef-building coral proxy archives as they provide century-scale highresolution climate information from extratropical regions. For
millennial-scale reconstructions extratropical marine sediments
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A.D. Wanamaker Jr. et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 302 (2011) 1–9
have yielded temporally extensive records; however, annual resolution data can be extracted only in rare circumstances (e.g.,
Baumgartner et al., 1992). While a variety of additional highly
resolved marine climate proxy archives exist from relatively shallow
extratropical seas (e.g., otoliths, statoliths, and non-tropical shallow
water corals), this brief introduction and accompanying special issue
will focus on the utilization of bivalves, coralline algae, and highresolution marine sediment cores in paleoclimate and environmental
studies within the most recent millennium with a focus on the
Northern Hemisphere (see Figs. 1 and 2).
2. Ocean and climate records from bivalve mollusks
Shortly after the discovery of utilizing reef-building corals as sea
surface temperature (SST) archives (Hudson et al., 1976) a number of
coral-based temperature reconstructions were developed (e.g.,
Dunbar and Wellington, 1981; Emiliani et al., 1978). At about the
same time, the potential of generating climate reconstructions from
mid-latitude bivalve records was recognized by Jones (1981). Major
advancements in bivalve sclerochronology and bivalve proxy development accelerated in the early 1980s (see Arthur et al., 1983; Jones,
1980; Rhoads and Lutz, 1980) and steady progress has continued for
the last two decades resulting in several century-scale climate
reconstructions from the North Pacific and the North Atlantic (e.g.,
Black et al., 2009; Butler et al., 2009a; Schöne et al., 2003; Strom et al.,
2004; Wanamaker et al., 2008a). At present, sclerochronological
analyses of bivalve mollusks supply the bulk of annual to sub-annual
resolution extratropical marine climate data for near-surface water
masses.
The motivation to use bivalve records in climate and ocean studies
originates from their great utility as environmental recorders (see
Rhoads and Lutz, 1980; Richardson, 2001). Bivalves are distributed
globally, inhabit a wide variety of environments and water depths,
and their fossilized shells are abundant and widely available through
geologic time (e.g., Krantz et al., 1987). Bivalves are often wellrepresented and often adequately preserved in archaeological sites,
providing a powerful means for investigating past environments and
cultures (e.g., Quitmyer and Jones, 2009; Quitmyer et al., 1997;
Sandweiss et al., 2001; Walker and Surge, 2006). A number of bivalve
species are extremely long-lived, with lifetimes of many decades or
even multiple centuries, some of which include freshwater pearl
mussels (Schöne et al., 2004a), geoduck clams (Strom et al., 2004),
ocean quahogs (Schöne et al., 2005a; Wanamaker et al., 2008b) and
deepwater oysters (Wisshak et al., 2009), making them ideal
candidates for climate studies. Further, bivalves deposit internal growth
increments in their shells with tidal to annual periodicities (Clark, 1976;
Jones, 1980; Richardson, 1989), thus paleo-environmental reconstructions can be temporally constrained with sub-seasonal to annual
resolution (Jones and Quitmyer, 1996). In fact, with cross-dating
techniques developed in dendrochronology, master shell growth
chronologies can be absolutely-dated and span several centuries or
more in length (Black et al., 2009; Butler et al., 2009a).
It has been shown that marine climate conditions such as seawater
temperature (e.g., Black, 2009; Black et al., 2009; Klein et al., 1996;
Lazareth et al., 2003; Schöne et al., 2004b, 2005a; Strom et al., 2004;
Wanamaker et al., 2008a; Weidman et al., 1994), seawater temperature seasonality/paleo-weather (e.g., Andreasson and Schmitz, 1996;
Bojar et al., 2004; Goewert and Surge, 2008; Jones and Allmon, 1995;
Patterson et al., 2010; Schöne and Fiebig, 2009; Schöne et al., 2005b),
ocean upwelling (e.g., Andrus et al., 2005; Jones et al., 2009b, 2010),
ocean 14C reservoir ages (e.g., Butler et al., 2009a; Jones et al., 2007;
Wanamaker et al., 2008b; Weidman and Jones, 1993), atmosphere/
ocean carbon dynamics (Butler et al., 2009a), productivity patterns
(e.g., Wanamaker et al., 2009; Witbaard et al., 2003), and oceanic/
atmospheric circulation patterns (e.g., Ambrose et al., 2006; Black,
2009; Black et al., 2009; Lazareth et al., 2006; Müller-Lupp and Bauch,
2005; Schöne et al., 2003; Wanamaker et al., 2008a; Weidman and
Jones, 1993) may be reconstructed from bivalve growth and
geochemical records. Recent advances in bivalve sclerochronology
(and in the field of sclerochronology) will likely facilitate a more
comprehensive assessment of marine climate variability and global
change issues, including anthropogenic impacts. For example,
geochemical records (stable carbon isotope ratios) derived from the
shells of marine bivalves (also sclerosponges and coralline algae)
indicate that the increased burning of fossil fuels in the last 100 years,
and the resultant CO2 emissions, have already noticeably changed the
stable carbon isotopic composition (negative trend) of the surface
waters in the oceans (see Böhm et al., 2002; Butler et al., 2009a; Swart
et al., 2010; Williams et al., 2011). Additionally, a recent study using a
marine sediment core collected within Loch Sunart (Scotland) by Cage
and Austin (2010) showed a pronounced negative shift in the stable
carbon isotopic composition of benthic foraminifera in the last
100 years. An important note of the Cage and Austin (2010) study is
that they used other calcifying organisms (foraminifera), which are
not impacted by ontogenetic growth trends like bivalves. Although
the interpretation of stable carbon isotope ratios derived from
bioarchives is often complicated by regional hydrographic variability
and local productivity patterns, a global trend is emerging. This
phenomenon is currently described as the δ13C Suess effect (after
Suess, 1953), and results from the admixture of isotopically negative
carbon derived from fossil fuels with Earth's modern atmospheric
carbon inventories. As expected, the changes in the stable carbon
isotopic composition of oceanic dissolved inorganic carbon (δ13CDIC)
pools, reflecting the atmospheric stable carbon isotopic trends
(δ13CAtm), are slightly attenuated. Further, the magnitude and timing
of the so-called δ13C Suess effect, as evidenced by marine proxy
Fig. 1. Overview map of study sites, types of archives used, and respective studies included in this special issue. Shaded rectangles indicate study regions, black dots individual study
sites.
A.D. Wanamaker Jr. et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 302 (2011) 1–9
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Fig. 2. Paleoclimate archives discussed in this issue. (A) Live- and dead-collected Arctica islandica shells from the Gulf of Maine. (B) High-resolution microscope photomosaic (from
an acetate replica) of internal growth increments in A. islandica from the hinge region showing the juvenile phase (right), juvenile to adult phase (middle), and mature phase (left).
Direction of shell growth is upward in each photo (C) Clathromorphum nereostratum growing attached to the seafloor at ~ 10 m water depth, Aleutian Islands, Alaska. (D) Digitized,
high-resolution photomosaic of a coralline alga (C. nereostratum) from the Aleutian Islands, Alaska. Thin red lines represent digitally mapped annual growth lines. Uppermost layer
represents year of collection. Black cavities are sporangial conceptacles (reproductive structures) forming annually. (E) Detail of sediment core section from a gravity core sampled
on the north Iceland shelf. Laminations indicate deposition of tephra layers. Images from Wanamaker, Hetzinger, Halfar, and J. Eiríksson.
records, is variable spatially, which is indicative of the spatiotemporal
variations in carbon fluxes and carbon sequestration in the global
ocean (e.g., Grottoli and Eakin, 2007). The next logical step would be
to use these data in carbon sequestration models (and data-model
comparisons) to improve our collective understanding of how past
and present anthropogenic CO2 is being cycled and stored in the
global ocean (see Quay et al., 1992; Swart et al., 2010).
2.1. Bivalve studies included in this issue
There are five papers in this issue using bivalve sclerochronology
to investigate ocean and climate dynamics. Four of these studies
present information from the long-lived marine bivalve Arctica
islandica (ocean quahog) from the temperate North Atlantic, while
one study provides environmental data from the Arctic bivalve
Clinocardium ciliatum (hairy cockle) in the Barents Sea (see Fig. 1). In
the study by Carroll et al. (2011-this issue), the authors use shell
growth data from 22 live-caught C. ciliatum specimens from three
stations in the Barents Sea to establish the impact of oceanographically distinct water masses on shell growth, and to determine the
influence of climatic forcing on ecological processes over decadal
scales. The authors reported that bivalve growth was substantially
different between populations largely living in Atlantic waters versus
Arctic waters (i.e., along the oceanic Polar Front), with bivalve growth
rates highest in Atlantic water. In the study of Butler et al. (2011-this
issue), the authors investigated the stable carbon isotope (δ13Cshell)
dynamics of A. islandica to determine if there were any consistent
ontogenetic effects on δ13Cshell values. The authors concluded that after
several decades of life, the δ13Cshell signature becomes stable and is not
impacted by age-related effects; hence the “relatively mature” δ13Cshell
values are likely valid measures of ambient dissolved inorganic carbon
(DIC) levels. On a similar note, Schöne et al. (2011-this issue;
contribution 1) illustrated δ13Cshell values from A. islandica shells
collected from northern Iceland and the Gulf of Maine during the
interval of AD 1750 to AD 2003. The authors suggested that the longterm δ13Cshell values declined in correspondence with ambient
atmospheric δ13C trends (i.e., the oceanic δ13C Suess effect). In the
Gulf of Maine, Wanamaker et al. (2011-this issue) reconstructed past
seawater temperature seasonality estimates for intervals during the last
millennium using A. islandica shells. The main finding reported by the
authors was a marked increase (~21%) in seawater temperature
seasonality during the early Little Ice Age as compared to Medieval
times. Also utilizing the geochemical signature from A. islandica shells,
Schöne et al. (2011-this issue; contribution 2) investigated the potential
of Mg/Ca and Sr/Ca ratios as seawater temperature proxies. The authors
suggested that after ontogenetic trends were removed from the
geochemical data, Mg/Ca and Sr/Ca ratios from shell material are viable
seawater temperature indicators.
3. Ocean and climate records from coralline algae
Coralline algae are the most recently developed proxy archive
discussed in this issue. While coralline algae are distributed in marine
habitats from polar to tropical latitudes and from intertidal shores to
the deepest reaches of the euphotic zone (Nelson, 2009), they have
received comparably limited attention, necessitating a brief overview
of their general occurrence and characteristics. Often they are a
dominant component of benthic communities and play a major role in
the ecology and development of most hard and soft substrates
throughout the world (Adey and Macintyre, 1973; Kuffner et al., 2007;
Steneck, 1986). Coralline algae can occur attached to a substrate or in
a free-living mode of life, where they are called rhodoliths (Bosence,
1983). In the tropics coralline algae form independent buildups, socalled algal ridges (Steneck et al., 2003), cement tropical coral reefs
(Adey, 1998) and provide the sedimentary infill to reef frameworks
(Dullo and Hecht, 1990). Outside the coral-reef belt coralline algae are
the most important framework builders (Freiwald and Henrich,
1994). Similar to corals and bivalves, individual plants of coralline
algae can live for hundreds of years, while forming annual growth
increments in their calcified thallus (i.e., skeleton) (Frantz et al., 2005;
Halfar et al., 2007). In contrast to bivalves, where sclerochronological
interpretations are complicated by a slowdown of growth with
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increasing shell age (Goodwin et al., 2003), corallines possess no
ontogenetic decrease of growth. A number of studies have now
demonstrated that crustose coralline algae are well suited as
recorders of extratropical paleoenvironmental signals because they
(1) are widely distributed in mid- and high-latitude oceans, (2) can
live for several centuries and (3) display well-developed growth
increments in a high-Mg calcite skeleton (Burdett et al., 2011-this
issue; Halfar et al., 2011-this issue; Hetzinger et al., 2011-this issue).
The feasibility of using a variety of species of both free-living,
branching and encrusting, massive coralline algae as proxy archives
has been confirmed during independent field calibration studies in
the temperate North Atlantic (Halfar et al., 2008; Kamenos et al.,
2008). The massive growing coralline Clathromorphum sp. which is
widely distributed in both the subarctic North Pacific and North
Atlantic can attain a thickness of more than 30 cm (Lebednik, 1976).
As mean annual growth increment widths of Clathromorphum sp.
range from 230–330 μm (Halfar et al., 2011-this issue; Hetzinger et al.,
2011-this issue) multicentury-scale coralline algal derived climate
records are possible.
3.1. Coralline algal temperature proxies
Early studies indicated that cyclic variations in the Mg-content of
coralline algae are related to water temperature fluctuations (Chave and
Wheeler, 1965) and growth rates (Moberly, 1968). The Mg–temperature
relationship was confirmed for temperate (Lithothamnion glaciale) and
subtropical (Lithothamnion crassiusculum) corallines by comparing Mg/
Ca ratios with oxygen isotopes and local SST (Halfar et al., 2000). Using Xray absorption near edge structure (XANES), Kamenos et al. (2008)
demonstrated that Mg is bound to the calcite lattice of analyzed coralline
algae (L. glaciale and Phymatolithon calcareum) and therefore not
associated with organic components, further confirming the use of
coralline algae as robust Mg-palaeotemperature proxies. This is
supported by a calibration study using electron and ion microprobes
that found highly significant linear relationships between MgCO3 and
SrCO3 (mol%) and SST (Kamenos et al., 2009). Similarly, significant
correlations with late spring to late fall instrumental SST were found in a
65-year long time series of electron microprobe-based Mg/Ca ratios
generated from Clathromorphum nereostratum collected in the Bering
Sea, Alaska (Hetzinger et al., 2009). Mg/Ca ratios in this sample relate well
to a 30-year δ18O time series measured on the same specimen. In the
Canadian Atlantic, Mg/Ca ratios of Clathromorphum compactum were
shown to be positively related to both station-based and gridded
instrumental SST (Gamboa et al., 2010). The 116-year long Atlantic algal
record suggests a variable negative relationship between Newfoundland
shelf SSTs and the North Atlantic Oscillation (NAO, see Jones et al., 1997)
which is strongest after ~1960 and before the mid 1930s.
The oxygen isotopic composition of coralline algae has been the
subject of numerous studies since the 1960s when oxygen isotopes
were found to be significantly offset from so-called equilibrium values
(Keith and Weber, 1965; Wefer and Berger, 1991). Rahimpour-Bonab
et al. (1997) compared the geochemistry of modern cool-water
corallines with their tropical counterparts. They found that the δ18O
values of algae from temperate environments could be used as a
paleotemperature proxy, because unlike their tropical counterparts
they deposit carbonate in isotopic equilibrium with ambient seawater. This, however, was not confirmed by Halfar et al. (2000, 2007,
2008), who found a significant negative isotopic offset in coralline
algae from subarctic Newfoundland (L. glaciale), Gulf of Maine (C.
compactum) and Alaska (C. nereostratum). However, Halfar et al.
(2000, 2007) and Hetzinger et al. (2009) demonstrated a strong
temperature dependence of algal δ18O ratios by comparison with
regional sea surface and air temperatures as well as Mg/Ca ratios
measured in the same specimens. A century-scale algal δ18O record (C.
nereostratum) yielded the first annually-resolved shallow marine
climate reconstruction from the subarctic North Pacific/Bering Sea
region (Halfar et al., 2007). In this case, microscope-based growthincrement counting in combination with U/Th dating was successfully
used to confirm the age and the continuous growth of a 117-year old
specimen of C. nereostratum (Halfar et al., 2007). The time series
shows significant spectral power at frequencies typical for the El
Niño-Southern Oscillation bandwidth (4–5.5 years) and is significantly correlated to the Pacific Decadal Oscillation, the dominant
climate pattern in the northern Pacific (e.g., Mantua et al., 1997).
Coralline algal growth and cell calcification have the potential to
preserve environmental signals as they are related to temperature and
light variability (Adey, 1970). Accordingly, Kamenos and Law (2010)
analyzed cell-wall thickness in both, laboratory-grown specimens and
50-year long time series of branched rhodoliths (L. glaciale). Results
showed that the thickness of cell-wall calcification in less extensively
calcified cells within annual growth increments is negatively
correlated to summer temperature. In addition, the time series
indicates negative correlations between the Atlantic Multidecadal
Oscillation (AMO, see Delworth and Mann, 2000) and cell-wall
thickness in both more- and less-extensively calcified cells for all
branches. However, Kamenos and Law (2010) observed no consistent
relationship between growth increment widths, temperature, cloud
cover and the AMO.
The above summary shows that environmental information is
preserved in the abundant and ubiquitous coralline algae, yet this
archive remains largely underutilized. Coralline algae have the
potential to yield numerous environmental records from regions
where other long-lived biogenic proxy archives with annual resolution are absent.
3.2. Coralline algal studies included in this issue
Specimens initially studied by Kamenos and Law (2010) were
reinvestigated by Burdett et al. (2011-this issue). The authors
demonstrate a weak statistically significant negative relationship
between less extensively calcified cells (summer growth) and winter
cloud cover as well as annual and summer SST. From this, Burdett et al.
(2011-this issue) present a cloud cover hindcast using summer
calcification data and SST. The authors suggest a modest rise in cloud
cover from 1910 to 2006. No consistent relationships between annual
growth increment widths and temperature or cloud cover were
observed in Kamenos and Law (2010) and Burdett et al. (2011-this
issue). In contrast, by combining growth increment width records of
multiple modern and museum collected specimens of C. compactum
from a broad geographic region in the subarctic northwest Atlantic,
Halfar et al. (2011-this issue) produced a 115-year composite algal
growth time series that is strongly related to regional SST patterns.
Finally, a laser ablation inductively coupled plasma mass spectrometry
(LA-ICP-MS) study investigated the use of certain metal/Ca ratios (Mg/
Ca, Sr/Ca, Ba/Ca, and U/Ca) as paleotemperature proxies for North Pacific
and Atlantic corallines of the genus Clathromorphum (Hetzinger et al.,
2011-this issue). While Mg/Ca ratios are strongly temperature controlled, correlations between Sr/Ca time series and SST data for both
study sites are positive but weak. Relationships between SST and U/Ca or
Ba/Ca are negative and largely statistically insignificant.
4. Ocean and climate records from high-resolution marine
sediment archives
Marine sediments archive paleoenvironmental change in the
oceans through time. During the past few decades paleoceanographic
and climatic reconstructions have been conducted based on marine
sedimentary records from all ocean basins. These efforts have
provided unique insights into the changing states of the past ocean
system. Using sophisticated techniques, information on past SST
variability can be obtained from the chemical composition or
abundance of organisms contained in the sedimentary records, by
A.D. Wanamaker Jr. et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 302 (2011) 1–9
analyzing the species abundance and faunal assemblage of planktonic
foraminifera and diatoms (CLIMAP, 1976), oxygen isotopic compositions of planktonic and benthic foraminifera, or more recently, the
ratios of Mg/Ca and Sr/Ca in foraminiferal shells (Lea et al., 1999;
Nürnberg et al., 1996; Rosenthal et al., 2004) or the ratio of certain
organic molecules (e.g., alkenones produced by coccolithophorids;
Keigwin, 2002; Kennett et al., 2000; Müller et al., 1998; Weldeab et al.,
2007).
By applying these paleoceanographic tools, SST records with
temporal resolutions ranging from decadal to centennial have been
generated allowing an assessment of past ocean and climate dynamics
over the recent millennia, and changes in large-scale ocean circulation
(e.g., Boyle and Keigwin, 1982; Bull et al., 2000; Keigwin, 2002). Such
reconstructions have provided a more detailed view on large-scale
surface ocean conditions during multi-century warm/cold episodes in
the Northern Hemisphere climate, which have been documented by
other land-based climate archives. For example, major efforts have been
undertaken to better characterize distinct periods of change during the
past millennium, such as the Medieval Climate Anomaly (MCA) and the
Little Ice Age (LIA) (e.g., deMenocal et al., 2000; Eiríksson et al., 2006;
Keigwin, 1996; Keigwin and Pickart, 1999; Lund et al., 2006; Mann et al.,
2009). However, many marine sedimentary proxy records often have
been difficult to combine with annually-resolved reconstructions from
other high-resolution archives (e.g., bivalves, corals, tree-ring, ice core,
and documentary sources) due to the commonly coarser temporal
resolution (centennial- to millennial-scale), and larger uncertainties in
underlying age models/dating techniques.
Recently, an increasing number of marine sedimentary records
with age control sufficient to reconstruct multidecadal-to-century
scale variations have been produced, and collaborative efforts to
further improve age models/dating techniques are underway (see
Jones et al., 2009a). Annually laminated (“varved”) marine sediments
can yield quantitative paleoclimatic reconstructions with annual and
even seasonal resolution (e.g., Romero et al., 2009; Sancetta and
Calvert, 1988; Thunell et al., 1993). The preconditions for the
accumulation of these sediments are a seasonally heterogeneous
supply of sediments and a lack of physical or biological reworking
(e.g., environments where bottom water oxygen content is persistently low enough to prevent burrowing organism from disturbing
the laminae) (Grimm et al., 1996). Such conditions are common in
settings that are dominated by coastal upwelling or in sedimentary
basins with restricted circulation. Numerous studies have described
laminated hemipelagic sediments from sites around the world in
continental margin settings including the basins off Southern
California (e.g., Santa Barbara Basin) (Behl and Kennett, 1996; Bull
et al., 2000; Kennett and Ingram, 1995; Nicholson et al., 2006), the
Gulf of California (Barron et al., 2004; Calvert, 1966; Pike and Kemp,
1997; Sancetta, 1995), the Saanich and Effingham Inlet (British
Columbia) (Chang et al., 2003; Chang and Patterson, 2005; Dean and
Kemp, 2004; Sancetta and Calvert, 1988), and the Cariaco basin off
Venezuela (Black et al., 2004, 2007; Haug et al., 2001; Hughen et al.,
1996; Peterson et al., 1991).
At present only a small number of ultra-high resolution marine
sedimentary archives have been retrieved that allow the reconstruction of climate and ocean changes on seasonal to interannual scales
(e.g., Baumgartner et al., 1992; Chang and Patterson, 2005; Dean and
Kemp, 2004). High-resolution sediment cores from the extratropical
North Atlantic have been used for reconstructions of marine surface
conditions (Cage and Austin, 2010; Eiríksson et al., 2006; Jiang et al.,
2005; Keigwin and Pickart, 1999; Keigwin et al., 2003; Knudsen and
Eiríksson, 2002; Kristensen et al., 2004; Richter et al., 2009). Because
the north Icelandic shelf is situated near strong oceanographic and
atmospheric climatic fronts, which separate temperate and Arctic
conditions (Johannessen, 1986), it has been a focal point of marine
sedimentary research providing exceptional archives capturing
surface ocean variability at interannual to decadal time scales (see
5
Sicre et al., 2008). Due to the distinct atmospheric and oceanic
conditions along the oceanic Polar front, the region near Iceland is
highly sensitive to climatic changes, where even minor changes in the
distribution of water masses translate into major environmental/
ecologic changes. These changes are then archived in high-resolution
marine sediments. The north Icelandic shelf is characterized by a
series of sedimentary basins, some of which have extremely high
sedimentation rates allowing sufficient temporal resolution for
assessing past changes in oceanography and climate with high
accuracy (e.g., Knudsen et al., 2009). The environmental changes on
the Icelandic shelf have been intensively studied throughout the last
decade, often with special emphasis on reconstructing the oceanic
climate of the last few millennia (e.g., Andrews and Giraudeau, 2003;
Andrews et al., 2001; Eiríksson et al., 2000, 2006; Jiang et al., 2005,
2007; Knudsen and Eiríksson, 2002; Knudsen et al., 2004, 2009; Ran et
al., 2008; Sicre et al., 2008). The presence of well-known tephra layers
from volcanic eruptions in Iceland has allowed the development of
more precise tephro-chronological age models on marine cores (e.g.,
Eiríksson et al., 2004, 2011-this issue; Larsen et al., 2002), thus
reducing uncertainties associated with radiocarbon dating. Due to
these advantages, ocean sediment records from this region have
provided a precise temporal constraint (within decadal accuracy) in
the northern North Atlantic with respect to the timing of the MCA/LIA
transition from the marine setting, which appears to have occurred at
~AD 1300 (Sicre et al., 2008). Interestingly, these data from the
marine environment and from compilations of glacial advances from
the Swiss Alps (Holzhauser et al., 2005; Schaefer et al., 2009) suggest
that the onset of the LIA in the Northern Hemisphere occurred prior to
a major reorganization in the North Atlantic Oscillation around AD
1450 (e.g., Trouet et al., 2009). Hence marine records with highly
constrained chronologies can offer important information regarding
the timing and phasing of climate change events between the
terrestrial and marine environments.
4.1. Marine sediment studies included in this issue
Two studies in this issue use sediment records from the north
Iceland shelf to investigate paleoceanographic changes during the last
millennium. In the study by Eiríksson et al. (2011-this issue), the
authors use two high-resolution sediment records to demonstrate a
coupling of changes in marine reservoir ages and paleoceanographic
shifts on the north Iceland shelf. To assess this relationship, deviations
between a tephro-chronological age-depth model and calibrated
mollusk-based AMS radiocarbon age determinations are compared
to various high-resolution palaeoclimatic proxies (e.g., benthic
foraminifera, ice-rafted debris). Eiríksson et al. (2011-this issue)
report considerable changes in average reservoir ages through time,
which the authors suggest is related to the changing influence of cold
Polar and Arctic water masses onto the north Iceland shelf. Ran et al.
(2011-this issue) reconstruct paleoceanographic changes on the north
Iceland shelf using precisely dated and high-resolution diatom
records. The diatom-based record of reconstructed summer SST is
compared to instrumental and documentary data for the last 100 years
to test its reliability. Temperature changes during the past millennium
are discussed with special focus on the MCA, the LIA, and the 20th
century warming on the north Iceland shelf. In general, the diatombased record from the north Iceland shelf shows high correspondence
to other proxy-based paleo-records in the North Atlantic region.
5. Conclusions and future outlook
A current challenge in climate and ocean studies is accessing and
providing annually-resolved and absolutely-dated records from
climatically important regions in the oceans to characterize recent
and past changes in ocean circulation, carbon cycle dynamics, and
climate change. Recent advancements in the field of sclerochronology
6
A.D. Wanamaker Jr. et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 302 (2011) 1–9
are beginning to contribute to this challenge. Using techniques
developed in dendrochronology, sclerochronologists have now
developed several cross-dated, annually-resolved, continuous master
shell chronologies of substantial length from the marine environment
(see Black, 2009; Black et al., 2008, 2009; Butler et al., 2009a,b;
Helama et al., 2006, 2007; Marchitto et al., 2000; Schöne et al., 2003;
Scourse et al., 2006; Strom et al., 2004; Stott et al., 2010; Witbaard
et al., 2003). Current and ongoing work utilizing coralline algae as
high-resolution marine climate archives is promising. Coralline algae
are long-lived, globally distributed, and occupy a variety of marine
habitats and water depths; hence coralline algal records can be used
to reconstruct a wide-range of marine environments, including
regions were other bioarchives are absent. Additionally, highresolution marine-based sedimentary archives from climatically
sensitive regions (e.g., near Iceland) that have excellent age/depth
chronological constraints (e.g., tephro-chronological age models) are
providing key insights about the timing and magnitude of rapid
climate change events during the last millennium (see Eiríksson et al.,
2011-this issue; Ran et al., 2011-this issue). These marine-based
records have the potential to substantially improve our understanding
of past global climate change events, by more thoroughly representing the ocean climate system.
Future research using bivalves, coralline algae, and high-resolution
marine sediment proxy archives should not only include further
proxy calibration with instrumental series, but should also involve
multi-proxy approaches using a combination of several archives.
Helama et al. (2007) were one of the first to compare a master shell
chronology (A. islandica) to a master tree-ring chronology (Scots pine;
Pinus sylvestris) from northwest Norway. From this work, Helama et
al. (2007) established that a modern, contemporaneous relationship
between shell and tree growth existed during strong NAO years.
However, they concluded that the two proxies may have behaved
differently in the past. Further, Black et al. (2009) combined geoduck
clam growth data with tree-ring observations to create an improved
reconstruction of the Pacific SST. Additionally, Felis et al. (2010)
combined geoduck clam growth data with coral-based geochemical
data in the Pacific Northwest and reported that by combining multiple
proxies from one region, the proxy-based compilation better reflected
the major climate pattern (Pacific Decadal Oscillation) (also see
Gedalof et al., 2002). In the Atlantic, marine proxy reconstructions
from the bivalve A. islandica and coralline algae were compared by
Halfar et al. (2008). Such records are critical in assessing possible
anthropogenic-induced changes in oceanic, atmospheric, and terrestrial systems. At present, the majority of marine climate reconstructions rely on time series that are based on individual records extracted
from single specimens, which prevents the quantitative separation of
the desired climate signals from noise at a given site (e.g., Jones et al.,
2009b). Hence, similar to dendrochronology, future sclerochronologic
studies of mid- and high-latitude archives should focus on constructing master growth chronologies (with substantial replication) with an
emphasis on using multispecimen approaches. Considering the recent
advancements in the construction of shell-based and coralline algal
chronologies (see Butler et al., 2010; Halfar et al., 2011-this issue), it
will be possible to develop regional networks (e.g., North Atlantic
network, North Pacific network) similar to tree-ring networks, to
evaluate regional responses to climate and ecosystem changes based
on master shell growth/coralline algae chronologies. Furthermore,
such networks would allow a direct comparison between shell and
tree-based records to determine temporal (lead/lag) relationships
between the marine and terrestrial environments as a result of
climate variability (see Black, 2009; Helama et al., 2007).
Acknowledgments
This paper and special issue resulted from a topical session at the
European Geosciences Union (EGU) General Assembly 2009 (Recon-
structing mid- to high-latitude climate and ocean variability from
high-resolution biogenic archives; CL19). We thank two anonymous
reviewers for their thoughtful comments and suggestions.
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