Potential and limitation of combining terrestrial and marine growth records from Iceland

• Published in: Global and planetary change Vol. 155; pp. 213 - 224
• Main Authors: Piermattei, A., Urbinati, C., Tonelli, E., Eggertsson, Ó., Levanič, T., Kaczka, R.J., Andrew, C., Schöne, B.R., Büntgen, U.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.08.2017
• Subjects: Annual growth increments; Arctica islandica; Betula pubescens; Multi-proxy approach; North Atlantic; Sorbus aucuparia; Sorbus aucuparia; North Atlantic; Annual growth increments; Arctica islandica; Multi-proxy approach; Betula pubescens
• ISSN: 0921-8181; 1872-6364
• DOI: 10.1016/j.gloplacha.2017.07.010

Seasonally formed, perennial growth increments of various organisms may possibly contain information about past environmental changes, well before instrumental measurements occurred. Such annually resolved proxy records have been mainly obtained from terrestrial archives, with a paucity of similar data originating from marine habitats. Iceland represents ideal conditions to develop both, tree ring (dendro) and bivalve shell (sclero) chronologies from adjacent sites. Here we introduce the first network of Icelandic birch (Betula pubescens Ehrh.) and rowan (Sorbus aucuparia) dendrochronologies, as well as ocean quahog (Arctica islandica L.) sclerochronologies. In order to identify the dominant external drivers of tree and shell growth, we assess the common growth trends and growth extremes within and between the terrestrial and marine records, as well as relationships of both archives with instrumental-based meteorological indices. Capturing a strong signal of June–August mean air temperature, the dendrochronologies are significantly positively correlated to each other. The sclerochronologies, however, reveal much lower growth coherency, which likely results from different sampling strategies and growth habitats. Disagreement between the dendro- and sclerochronologies possibly originates from unequal sample size, offset in the seasonal timing and rate of the growth, as well as varying sensitivities to different environmental factors. Our results emphasize the importance of considering a wide range of species and taxa to reconstruct a more complete picture of terrestrial and marine ecosystem functioning and productivity across various spatiotemporal scales. Sampling sites of the dendro and sclero data (circles and triangles), with colors referring to their correlation coefficients (r) against mean monthly air temperature (Tmean) and sea surface temperature (SST), respectively. White and green areas on Iceland represent ice and woodland cover (Traustason and Snorrason, 2008). Values at each site location indicate the month of highest correlation (e.g. ‘6’=June, ‘6:7’=June–July, ‘−6’=June of the previous year). Values in square brackets at the four cardinal points are correlation coefficients (r) between Tmean and SST, at the pairings of Iceland's four geographical sectors, NW-SW, SW-SE, SE-NE, NE-NW. The first, left value refers to the seasonal length of shell growth (February–September), whereas the second, right value indicates the seasonal length of tree growth (June–August). Light blue shadings in the inset depict the natural distribution of Arctica islandica (modified after Dahlgren et al., 2000), with red and blue arrows representing warm and cold ocean currents, respectively. [Display omitted] •Iceland offers terrestrial (dendro) and marine (sclero) proxies from adjacent sites•Summer air temperatures control tree growth and synchronize dendro-chronologies•Little coherency between sclero-chronologies reflects complex environmental drivers•Offset between dendro- and sclero-chronologies provides reconstruction opportunities•Multi-proxy approach reveals complete picture of terrestrial and marine ecosystems