Physical and chemical impacts of a major storm on a temperate lake: a taste of things to come?

Extreme weather can have a substantial influence on lakes and is expected to become more frequent with climate change. We explored the influence of one particular extreme event, Storm Ophelia, on the physical and chemical environment of England’s largest lake, Windermere. We found that the substantial influence of Ophelia on meteorological conditions at Windermere, in particular wind speed, resulted in a 25-fold increase (relative to the study-period average) in the wind energy flux at the lake-air interface. Following Ophelia, there was a short-lived mixing event in which the Schmidt stability decreased by over 100 Jm^?2 and the thermocline deepened by over 10 m during a 12-h period. As a result of changes to the strength of stratification, Ophelia also changed the internal seiche regime of Windermere with the dominant seiche period increasing from ~?17 h pre-storm to ~?21 h post-storm. Following Ophelia, there was an upwelling of cold and low-oxygenated waters at the southern-end of the lake. This had a substantial influence on the main outflow of Windermere, the River Leven, where dissolved oxygen concentrations decreased by ~?48%, from 9.3 to 4.8 mg L^?1, while at the mid-lake monitoring station in Windermere, it decreased by only ~?3%. This study illustrates that the response of a lake to extreme weather can cause important effects downstream, the influence of which may not be evident at the lake surface. To understand the impact of future extreme events fully, the whole lake and downstream-river system need to be studied together.     

On the Tropical Rainfall Measuring Mission (TRMM)

Summary The importance of quantitative knowledge of tropical rainfall, its associated latent heating and variability is summarized in the context of climate change. Since the tropics are mainly covered with oceans, with some deserts and jungles, the monthly precipitation is not known within a factor of two. Hence the only way to measure it adequately for climate and general circulation models is from space. The paper describes the Tropical Rainfall Measuring Mission (TRMM). This joint Japan-U.S. cooperative Earth Probe satellite will be launched from Japan in 1997 for a three-year mission. The scientific basis of the instrument and orbit selection is explained. The precipitation instrument complement comprises the first rain radar to be flown in space (PR), and a multi-channel passive microwave sensor (TMI) improved relative to the SSM/I¹ by an additional channel at 10 GHz. The third rain instrument is a five-channel VIS/IR (VIRS) sensor. Progress in construction of instruments, observatory, data system, and the ground validation program is summarized. A report is also given concerning development of the algorithms by which rainfall and its associated latent heat release will be calculated from the several instruments, separately and in combination, and how the scientists will interact with the data system to obtain the 32 rain data products necessary to fulfill the science requirements.With 9 FiguresSSM/I stands for Special Sensor Microwave Imager.     

Banded structure of drifting macroalgae

A massive bloom of macroalgae occurred in the western Yellow Sea at the end of May, 2008, and lasted for nearly 2 months. The surface-drifting macroalgae was observed to accumulate in a pattern dominated by linear bands. The maximum length of individual algal bands exceeded 10 km and the distance between neighboring bands ranged from hundreds of meters to 6 km. Seven satellite images were analyzed to determine the distances between neighboring bands. Proportions of about 24%, 38%, and 22% are responsible for the separation distances smaller than 1 km, between 1 and 2 km, and between 2 and 3 km, respectively. The separation of about five percent of the bands exceeds 4 km. The probability distribution of the separation distance is quite close to log-normal which is that found in Langmuir circulation. However, the observed algal band separation greatly exceeds the distances between convergence lines reported in Langmuir circulation.     

Cultural sediment analyses and transitions in early fishing activity at Langenesværet,Vesterålen,Northern Norway

The development of specialized and commercial fishing activity in the island archipelago of Lofoten and Vesterålen in northern Norway is a critical foundation from which to understand the subsequent spread of commercial fishing across the north Atlantic region during the medieval and early modern period. One little understood aspect of this development is the relationship between medieval commercial fishing stations (fiskevaer) and earlier fishing activity. In this article, cultural sediment deposits at Langenesværet, Vesterålen, Northern Norway provide an opportunity to examine this relationship and its implications for current historical models of fishing development in northern Norway and the north Atlantic region. Conventional and AMS radiocarbon dating techniques are used to establish a chronology for the deposits, while activities associated with the sediments are characterized using thin‐section micromorphology supported by proton induced X‐ray emission spectrometry (PIXE). The results suggest that the site commenced formation as early as ca. 3000 B.C. and that the site was first used for specialized fishing activity from the early centuries A.D. The medieval commercial fiskevaer settlement at Langenesværet was introduced to an area that had a longstanding tradition of specialised fishing activity. © 2000 John Wiley & Sons, Inc.     

Local‐scale adaptations: A modeled assessment of soil,landscape, microclimatic,and management factors in Norse home‐field productivities

Adaptation of farming practices to inherent site conditions was essential to the success of Norse colonization in pristine landscapes. A key factor in the initial success of colonization, or landnám, of Iceland was management of the area adjacent to the domestic dwelling, the home‐field, to provide fodder for over‐wintering livestock. In this paper we examine three settlement home‐fields in the Mývatn and Laxá valley area of northeast Iceland. Contemporary evidence reveals a distinct climatic toposequence together with differences in the nature of the inherent soils between sites. By considering the influence of these differences, microscale adaptations in early land management practices in the production of hay are sought within a tightly defined chronological context. Using an integrated agroecosystem modeling approach, the factors affecting long‐term sustainability of hay production in the Norse home‐field are examined. Results indicate that regional‐level climate differences will have an impact on production, especially pronounced cold periods. It is also clear that small‐scale climate factors, as well as inherent soil differences between sites influenced productivity for the Norse farmer. However, productivities overall are at subsistence level, emphasizing the need for optimized land management to sustain home‐field production. After examining different management scenarios, it is apparent that the effect of an increased rate of manuring will be most apparent during the first century of settlement; thereafter the effect is relatively diminished. © 2008 Wiley Periodicals, Inc.