Recurrent transitions to Little Ice Age-like climatic regimes over the Holocene     

Helama  Samuli  Stoffel  Markus  Hall  Richard J.  Jones  Phil D.  Arppe  Laura  Matskovsky  Vladimir V.  Timonen  Mauri  N&#;jd  Pekka  Mielik&#;inen  Kari  Oinonen  Markku 《Climate Dynamics》2021,56(11):3817-3833

Holocene climate variability is punctuated by episodic climatic events such as the Little Ice Age (LIA) predating the industrial-era warming. Their dating and forcing mechanisms have however remained controversial. Even more crucially, it is uncertain whether earlier events represent climatic regimes similar to the LIA. Here we produce and analyse a new 7500-year long palaeoclimate record tailored to detect LIA-like climatic regimes from northern European tree-ring data. In addition to the actual LIA, we identify LIA-like ca. 100–800 year periods with cold temperatures combined with clear sky conditions from 540 CE, 1670 BCE, 3240 BCE and 5450 BCE onwards, these LIA-like regimes covering 20% of the study period. Consistent with climate modelling, the LIA-like regimes originate from a coupled atmosphere–ocean–sea ice North Atlantic-Arctic system and were amplified by volcanic activity (multiple eruptions closely spaced in time), tree-ring evidence pointing to similarly enhanced LIA-like regimes starting after the eruptions recorded in 1627 BCE, 536/540 CE and 1809/1815 CE. Conversely, the ongoing decline in Arctic sea-ice extent is mirrored in our data which shows reversal of the LIA-like conditions since the late nineteenth century, our record also correlating highly with the instrumentally recorded Northern Hemisphere and global temperatures over the same period. Our results bridge the gaps between low- and high-resolution, precisely dated proxies and demonstrate the efficacy of slow and fast components of the climate system to generate LIA-like climate regimes.

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Characteristic features of air ions at Mace Head on the west coast of Ireland     

Marko Vana  Mikael Ehn  Tuukka Petj  Henri Vuollekoski  Pasi Aalto  Gerrit de Leeuw  Darius Ceburnis  Colin D. O'Dowd  Markku Kulmala 《Atmospheric Research》2008,90(2-4):278-ICNAA07

Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.34–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameters smaller than 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in the marine coastal environment. Intermediate ion concentrations were generally close to zero, but during some nucleation episodes the concentrations increased to several hundreds per cm³. Nucleation events occurred during most of the measurement days. We classified all days into one of seven classes according to the occurrence and type of new particle formation. Nucleation events were observed during 207 days in 2006, most prominently in the spring and summer months. Rain-induced events, in turn, were observed during 132 days. Particle formation and growth events mostly coincided with the presence of low tide. Also small cluster ions (0.34–1.6 nm) were characterized. Average concentrations of small ions were 440 cm^− 3 for the negative ions and 423 cm^− 3 for the positive ions. Average mean mobilities of small ions were 1.86 cm²V^− 1s^− 1 and 1.49 cm²V^− 1s^− 1 for the negative and positive polarities, respectively. Concentrations of small ions were observed to be strongly dependent on the variations of meteorological parameters including wind speed and direction.  相似文献   

Power and influence tactics in the promotion of regional development: An empirical analysis of the work of Finnish regional development officers     

Markku Sotarauta 《Geoforum》2009,40(5):895-905

Increased complexity and rapid pace of change demand more from people responsible for regional development at various levels of activity. This paper has its roots in a belief that the more complex situations are, the more regional development is dependent on the leadership and network management capacity of key individuals. Studying more deeply the roles that various individuals, and the coalitions formed by them, have in institutionalisation, deinstitutionalisation and reinstitutionalisation processes might provide us with additional analytical leverage in regional development studies. This paper focuses on diffuse networks of dispersed powers from a Finnish regional development officer’s point of view. Regional development officers are those people whose job it is to boost the economic development of their respective regions in Finland.The research questions discussed here are: (a) What kind of power is exercised by Finnish regional development officers; and (b) how do regional development officers aim to gain influence for their efforts to promote regional development? The empirical research is based on data gathered (a) through 41 interviews with Finnish actors responsible for the promotion of economic development in city governments, technology centres, regional development agencies, and ministries and other national bodies, and (b) through internet survey of development officers at local, regional and national levels (531 respondents, response rate 51.8%). The survey was designed to solicit information about power and influence tactics in the context of regional development. The empirical analysis shows, for example, how interpretive power and network power are more important for regional development officers than institutional and resource power, and how indirect influence tactics surpass direct tactics.  相似文献   

Experimental determination of ventilation coefficient for 1-hexanol drops in air     

Ji í Smolík  Jaroslav Schwarz  Markku Kulmala 《Atmospheric Research》1998,46(3-4)

Two experimental techniques have been used for study of mass transfer from a drop of 1-hexanol evaporating into air. In the first technique, liquid is added to the drop by a supporting capillary. When the rate of liquid adding counterbalances the evaporation rate, the drop size remains constant and the evaporation takes place at steady state. In the second case with drop suspended from a thermocouple, the rate of evaporation is determined from variation of drop diameter with time. Since the combination of both methods should allow to measure at the broader range of experimental conditions, the differences and their impact on experimental determination of mass transfer are discussed. The results are compared with results of previous experimental and theoretical works reported in the literature.  相似文献   

Building a regime for climate protection: Finland and international climate policy     

Markku Wilenius  Juhani Tirkkonen 《Global Environmental Change》1998,8(4):291-308

The effective management of climate change on a national as well as an international level requires close co-operation between the scientific community and the political sector. Climate change first became a major subject of scientific inquiry in the early 1980s, and real political interest in the issue was awakened towards the end of that decade. In the last few years, the dialogue between the scientific community and the political sector has increased considerably. As a result, climate change is today one of the most significant areas in environmental research and international environmental policy alike.This paper examines the emergence and consolidation of international climate change regime. The theory of regime building is used as discussed by Young (1989). International Cooperation. Cornell University Press, Ithaca. The paper begins with an outline of the historical emergence of climate research and climate policy. This is followed by a discussion of the history and development of the Rio Convention, with a look at the latest developments in international climate politics. The next section begins with an examination of the foundations and present strategies of Finnish climate policy, which is used as a case study, and the paper concludes with an assessment of the current state of Finnish climate policy, illustrating the problems of compliance individual countries face when adopting the norms and principles of the regime.  相似文献   

A study of the formation of high molecular weight compounds during the decomposition of a field diatom population     

E.-L. Poutanen  R.J. Morris 《Estuarine, Coastal and Shelf Science》1983,17(2):189-196

This work has investigated the possible formation of humic and fulvic acids, particularly high molecular weight moieties, in degrading diatom debris. The diatom debris was collected, freshly sedimented, from a well characterized natural field diatom population and allowed to degrade under conditions similar to those found at the sediment-water interface of many marine, organic-rich sediments.Samples of the detritus and overlying water were taken regularly over a period of 4 months and analysed for the presence of humic compounds. In the case of the detrital material, a sequential series of extractions were used. Molecular weight fractionation of the extracted humic material was carried out using Diaflow Ultrafiltration Membranes and two different fractionation methods have been compared. It appears that the choice of method may have an important effect on the determined distribution of the humic material, particularly when humic acid concentrations are low.High molecular weight (> 300 000- > 100 000) humic and fulvic acids were found in all the detrital samples, the content increasing with the period of decomposition. No evidence of any humic material was found in extracts of the living diatoms, the conclusion being that this material had been formed in situ during the degradation of the diatom debris. Most (65–90%) of the humic material was extracted from the detritus using a mild 0·05 m NaOH extraction at room temperature. Fulvic acids comprised approximately 90% of the total 0·05 m NaOH extraction, being composed mainly of either low molecular weight compounds (40–50% < 10000) or high molecular weight compounds (38–48% > 100000). Levels of humic acids were much lower and included a wide range of molecular weight fractions.The relevance of these findings to the possible origin of humic material in certain marine sediments is discussed.  相似文献   

Size-resolved characteristics of inorganic ionic species in atmospheric aerosols at a regional background site on the South African Highveld     

Andrew D. Venter  Pieter G. van Zyl  Johan P. Beukes  Jan-Stefan Swartz  Miroslav Josipovic  Ville Vakkari  Lauri Laakso  Markku Kulmala 《Journal of Atmospheric Chemistry》2018,75(3):285-304

Aerosols consist of organic and inorganic species, and the composition and concentration of these species depends on their sources, chemical transformation and sinks. In this study an assessment of major inorganic ions determined in three aerosol particle size ranges collected for 1 year at Welgegund in South Africa was conducted. SO₄^2? and ammonium (NH₄⁺) dominated the PM₁ size fraction, while SO₄^2? and nitrate (NO₃) dominated the PM_1–2.5 and PM_2.5–10 size fractions. SO₄^2? had the highest contribution in the two smaller size fractions, while NO₃^? had the highest contribution in the PM_2.5–10 size fraction. SO₄^2? and NO₃^? levels were attributed to the impacts of aged air masses passing over major anthropogenic source regions. Comparison of inorganic ion concentrations to levels thereof within a source region influencing Welgegund, indicated higher levels of most species within the source region. However, the comparative ratio of SO₄^2? was significantly lower due to SO₄^2? being formed distant from SO₂ emissions and submicron SO₄^2? having longer atmospheric residencies. The PM at Welgegund was determined to be acidic, mainly due to high concentrations of SO₄^2?. PM₁ and PM_1–2.5 fractions revealed a seasonal pattern, with higher inorganic ion concentrations measured from May to September. Higher concentrations were attributed to decreased wet removal, more pronounced inversion layers trapping pollutants, and increases in household combustion and wild fires during winter. Back trajectory analysis also revealed higher concentrations of inorganic ionic species corresponding to air mass movements over anthropogenic source regions.  相似文献