Spring production of Calanus finmarchicus at the Iceland-Scotland Ridge

Distribution and reproduction activity of the calanoid copepod Calanus finmarchicus were studied in the waters between Scotland and Iceland in April 1997 during the expected time of the animals' ascent to surface waters following diapause. Ascent was taking place on both sides of the Iceland-Scotland Ridge, apparently from two separate overwintering centers. The population on the Faroe Shelf (FS) most likely came from the overwintering population in the Faroe Shetland Channel (FSC). Per capita egg production was highest on the FS (> 30 eggs female -1d-1) and lowest in the Iceland Basin (10 eggs female -1d-1). The maximum clutch size recorded was on the FS (145 eggs). As the maximum clutch sizes that females produced were between 40% and 77% (area averages of the station maximum rates) of their size-specific reproduction potential, it is argued that egg production rates were generally food-limited. Chlorophyll a concentrations were, at all but one station, under 1 ugL-1. Chlorophyll-based ingestion could, theoretically, support the observed average egg production rates in the Iceland Basin and on the FS but only about 30% of the observed production at the stations in the East Icelandic Current (EIC). The carbon assimilated through ingestion of phytoplankton, Calanus own eggs andnauplii in the EIC was estimated to be too low to support the frequently observed production of clutches consisting of over 100 eggs. Cannibalism on eggs and nauplii was not likely to have constituted a significant component of dietary carbon intake. However, a combination of feeding and assimilation of reserved lipid remaining from overwintering could be sufficient to explain the observed per capita egg production rates. C. finmarchicus copepod stages 1-3 were only recorded in considerable numbers only on the FS. This suggests higher survival rates of eggs in the shelf waters

Tracing marine cryptotephras in the North Atlantic during the last glacial period: Protocols for identification, characterisation and evaluating depositional controls

Tephrochronology is increasingly being utilised as a key tool for improving chronological models and correlating disparate palaeoclimatic sequences. For many sedimentary environments, however, there is an increased recognition that a range of processes may impart a delay in deposition and/or rework tephra. These processes can affect the integrity of tephra deposits as time-synchronous markers, therefore, it is crucial to assess their isochronous nature, especially when cryptotephras are investigated in a dynamic marine environment. A methodology for the identification and characterisation of marine cryptotephras alongside a protocol for assessing their integrity is outlined. This methodology was applied to a wide network of North Atlantic marine sequences covering the last glacial period. A diverse range of cryptotephra deposits were identified and, based on similarities in physical characteristics (e.g. glass shard concentration profiles and geochemical homogeneity/heterogeneity), indicative of common modes of tephra delivery and post depositional reworking, a deposit type classification scheme was defined. The presence and dominance of different deposit types within each core allowed an assessment of spatial and temporal controls on tephra deposition and preservation. Overall, isochronous horizons can be identified across a large portion of the North Atlantic due to preferential atmospheric dispersal patterns. However, the variable influence of ice-rafting processes and an interplay between the high eruptive frequency of Iceland and relatively lower sedimentation rates can also create complex tephrostratigraphies in this sector. Sites within a wide sector to the south and east of Iceland have the greatest potential to be repositories for isochronous horizons that can facilitate the synchronisation of palaeoclimatic records

SSoelvsten/adiar: v2.0.0-beta.5

New Features Functional Bridge: Fully generalised and committed to the use of functions to bridge between Adiar and the user's code (as was started in v2.0-beta.2). To this end, Adiar now provides the types predicate and generator to pass information into Adiar and consumer to pass information back out again. All functions of v1.x that used some file, e.g. bdd_restrict, zdd_onset, bdd_varprofile etc. all now provide one (or more) of these functions instead. Execution Policy: Each algorithm (when relevant) has been overloaded with an exec_policy as its first argument. This class provides a thread-safe way of passing options into an algorithm, e.g. whether the algorithm should use internal or external memory data structures. This replaces the use of the globally set enum values, e.g. memory_mode. bdd_top(), bdd_bot(), zdd_top(...), and zdd_bot(...): Provide a uniform interface for getting the top and the bot value of the lattice. This provides a more uniform and interchangeable interface between BDDs and ZDDs where you do not need to think about the reduction rules. Optimisations bdd_satmin and bdd_satmax Stores the intermediate result in an internal memory stack (since it can at most be 8 MiB in size) rather than writing it out to disk. This should improve their performance slightly. Breaking Changes The function overloads with an auxiliary file as an input, e.g. bdd_restrict, zdd_onset, bdd_varprofile, have been removed in favour of the new functional input instead. The enums memory_mode, access_mode, and quantify_mode have been removed in favour of using the new Execution Policy. Removed the functions bdd_counter and zdd_sized_set. They may be added anew, assuming someone sends in a feature request. Fixed inconsistency of naming scheme in predicates. For example, the function is_true(const bdd &) has been renamed to bdd_istrue(const bdd&) to be consistent with the rest of the API. Removed the map_pair class introduced in v2.0-beta.2 as it has become redundant with the simpler function interface. Contributors Steffan Sølvsten ( @SSoelvsten