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Abstract The Iceland Scotland Overflow Water (ISOW) plume supplies approximately a third of the production of North Atlantic Deep Water and is a key component of the meridional overturning circulation (MOC). The Overturning in the Subpolar North Atlantic Program (OSNAP) mooring array in the Iceland Basin has provided high‐resolution observations of ISOW from 2014 to 2020. The ISOW plume forms a deep western boundary current along the eastern flank of Reykjanes Ridge, and its total transport varies by greater than a factor of two on intra‐seasonal timescales. EOF analysis of moored current meter records reveal two dominant modes of velocity variance. The first mode explains roughly 20% of the variance and shows a bottom intensified structure concentrated in the rift valley that runs parallel to the ridge axis. The transport anomaly reconstructed from the first mode explains nearly 80% of the total ISOW plume transport variance. The second mode accounts for 15% of velocity variance, but only 5% of the transport variance. The geostrophically estimated transport (2.9 Sv) recovers only 70% of the total ISOW transport along the ridge flank estimated from the direct current meter observations (4.2 Sv), implying a significant ageostrophic component of ISOW mean transport and variability. Ageostrophic flow is strongly linked to the leading mode of velocity variability within the rift valley. The ISOW transport variability along the upper and middle part of the ridge is further shown to correlate with changes in the strength of deep MOC limb across the basin‐wide OSNAP array.
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The Iceland Microcontinent and a continental Greenland-Iceland-Faroe Ridge
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null (Ed.)Abstract The Iceland Greenland Seas Project (IGP) is a coordinated atmosphere–ocean research program investigating climate processes in the source region of the densest waters of the Atlantic meridional overturning circulation. During February and March 2018, a field campaign was executed over the Iceland and southern Greenland Seas that utilized a range of observing platforms to investigate critical processes in the region, including a research vessel, a research aircraft, moorings, sea gliders, floats, and a meteorological buoy. A remarkable feature of the field campaign was the highly coordinated deployment of the observing platforms, whereby the research vessel and aircraft tracks were planned in concert to allow simultaneous sampling of the atmosphere, the ocean, and their interactions. This joint planning was supported by tailor-made convection-permitting weather forecasts and novel diagnostics from an ensemble prediction system. The scientific aims of the IGP are to characterize the atmospheric forcing and the ocean response of coupled processes; in particular, cold-air outbreaks in the vicinity of the marginal ice zone and their triggering of oceanic heat loss, and the role of freshwater in the generation of dense water masses. The campaign observed the life cycle of a long-lasting cold-air outbreak over the Iceland Sea and the development of a cold-air outbreak over the Greenland Sea. Repeated profiling revealed the immediate impact on the ocean, while a comprehensive hydrographic survey provided a rare picture of these subpolar seas in winter. A joint atmosphere–ocean approach is also being used in the analysis phase, with coupled observational analysis and coordinated numerical modeling activities underway.more » « less
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Identifying foreign cloth imports in the Icelandic archaeological corpus is difficult at best, yet given widespread similarities in homespun cloth from sites across the country, imported cloth can be identified visually through the presence of refined finishing techniques (such as teaseling, shearing, and fulling) that were uncommon in Iceland and were the products of specialist craftsmen in Europe. This paper examines textile assemblages from deposits datable to the period of Hanseatic trade at three sites, Gilsbakki, Reykholt, and Stóra-Borg that represent two wealthy, interior, parish centres and a moderate-sized coastal farm, respectively. Variations in the number and diversity of imported cloth items within these sites’ assemblages suggest that while Hanseatic material culture was widely spread on Icelandic rural sites, the nature of the material culture sub-assemblages attributable to Hanseatic trade was not obviously a direct function of households’ wealth or proximity to harbours but may have engaged other cultural factors linked to the political and social challenges of the post-Reformation period and the roles of individual households in regional or intra-Icelandic trade.more » « less
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Abstract Basaltic watersheds such as those found in Iceland are thought to be important sites of CO2sequestration via silicate weathering. However, determining the magnitude of CO2uptake depends on accurately interpreting river chemistry. Here, we compile geochemical data from Iceland and use them to constrain weathering processes. Specifically, we use a newly developed inverse model to quantify solute supply from rain and hydrothermal fluids as well as allow for variable silicate end‐member compositions, solutes to be removed via secondary phase formation, and some Ca to be sourced from carbonate dissolution. While some of these processes have been considered previously, they have not been considered together allowing us to newly determine their relative contributions. We find that weathering in Iceland is incongruent in two ways. First, solute release from primary silicates is characterized by a higher proportion of Na than would be expected from bulk basalts, which may reflect preferential weathering or some contribution from rhyolites. This Na enrichment is further enhanced by preferential Mg and K uptake by secondary phases. No samples in our data set (n = 537) require carbonate dissolution even if isotopic data (δ26Mg,δ30Si,δ44Ca, and/or87Sr/86Sr) are included. While some carbonate weathering is allowable, silicate weathering likely dominates. The complexity we observe in Iceland underscores the need for inverse models to account for a wide range of processes and end‐members. Given that riverine fluxes from Iceland are more Na‐rich than expected for congruent basalt weathering, the characteristic timescale of CO2drawdown is likely affected.more » « less
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Lake water chemistry was measured for lakes in Iceland. We used a multiparameter probe (HydroLab HL4, OTT HydroMet) to measure in situ temperature, pH, dissolved oxygen (DO), and electrical conductivity of the water column at 0.5-1 m resolution. These measurements were repeated during each field campaign, resulting in multiple years of summer water chemistry data for many lakes. For some lakes, profiles of the water column were additionally taken through the ice during a February field campaign. Additionally, 0.5-1L grab samples of surface and bottom waters were analyzed for Total Phosphorus (mg/L), Chloride (mg/L), Nitrate (mg/L), Sulfate (mg/L), TOC/DOC (mg/L), and Total Nitrogen (mg/L).more » « less
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1016/j.earscirev.2019.102926
