Unraveling environmental histories from skeletal diaries — Advances in sclerochronology

a r t i c l e i n f o Keywords: Sclerochronology Special issue Environmental proxies Decadal climate variability Resource management High-resolution proxy archives from aquatic settings are essential to better understand processes and mechanisms of global change. During the last decade, it has become increasingly evident that calcified tissues of bivalve mollusks and cold-water corals, in particular, can significantly increase our knowledge of seasonal to multi-decadal paleoclimate and paleoenvironmental variability in the extratropical oceans and coastal marine settings. Daily, tidal, fortnightly and annual growth patterns of periodically formed skeletal hard parts provide a means to place the proxy record in a precise temporal context. Their extreme longevity coupled with the running similarity between growth increment time-series of contemporaneous bivalves opens the possibility of constructing stacked chronologies covering centuries to millennia which provide information on decadal climate and environmental variability and magnitudes of climate variability through time. A current major research focus is on how to translate geochemical properties of the skeletons into quantifiable environmental proxy data and how to eliminate the adverse influence of vital effects on the proxy records. This special issue presents the most recent advances in the field of sclerochronology, specifically calcified tissues of bivalve mollusks, cold-water corals and tropical shallow water corals. The majority of the contributions deal with the potential reconstruction of temperature, pH and productivity through the analysis of 18 O and δ 44/40 Ca. Four papers present composite chronologies of two long-lived bivalve species and discuss inherent decadal climate variability, and one study demonstrates that sclerochronology can shed light on socioeconomic patterns of past human populations as well as resource use and resource management by people. Proxy records of paleoenvironmental conditions are essential to understand climate and ecosystem dynamics prior to the instrumental era (ca. 1860 A.D.; Jones et al., 2001, 2009). To draw a more detailed picture of the past, however, requires seasonally to annually resolved, precisely chronologically aligned and, most importantly, quantifiable proxy data from various geographical settings (IPCC, 2007). The majority of high-resolution (= annual to subannual) climate and environmental archives come from the terrestrial realm and largely capture atmospheric and/or continental conditions (e.g., tree-rings, speleothems, ice cores). By contrast, paleoenvironmental and paleoclimate records from marine settings are sparse and often have poor temporal resolution. However, well-constrained subannually resolved archives for the marine environment do exist, i.e. in the form of sclerochronological 1 archives. Shallow-water corals have been …