An analysis of extra-tropical storms in the North Atlantic region as simulated in a control and 2 × CO2time-slice experiment with a high-resolution atmospheric model
Abstract
The variability of an annual resolution deuterium time series from central Greenland is investigated in connection with the variability in the frequency of daily atmospheric circulation patterns in the North Atlantic region. Statistical analysis reveals that a large part of the decadal variability of the deuterium isotope record is related to decadal variability in the frequency of several identified daily circulation patterns. The study shows that these circulation patterns induce variations in the deuterium record by altering where isotopic fractionation occurs, mainly during the passage of the associated air masses over continental areas. The study identifies three significant periodic components in the deuterium isotope record at ∼12, ∼20, and ∼30 yr. It also shows that the ∼20-yr signal in the deuterium isotope record is related to the variability in the frequency of a winter circulation type. An analysis of six oxygen isotope records from central Greenland reveals decadal variations similar to the deuterium isotope record. The authors argue that high-resolution stable isotope records from Greenland ice cores can be used to obtain information about the frequency of certain daily circulation patterns during past periods.
This article describes a study of Tripleurospermum maritimum (L.) W.D.J. Koch and T. inodorum (L.) Sch. Bip. (Asteraceae) in the Orkney Islands (v.c.111), the results of which suggest that intermediates between these taxa may be rather common, and that T. maritimum subsp. nigriceps and subsp. maritimum are both involved, the former more frequently. Obviously this results in a complex taxonomic situation, evidently not confined to Orkney in the far north. Key identifying characters of the taxa are systematically examined and guidance offered on determining hybrids using a population level approach. The taxonomic complexities of these northern populations are discussed, with regard in particular to the identity of T. inodorum occurring there and the place of T. maritimum subsp. nigrescens in the forms and subspecies of T. maritimum found in the north Atlantic region.
Decadal Variability in a Central Greenland High-Resolution Deuterium Isotope Record and Its Relationship to the Frequency of Daily Atmospheric Circulation Patterns from the North Atlantic Region