Seasonal dynamics of water and nutrient fluxes in an agricultural peatland

The American cranberry (Vaccinium macrocarpon Ait.) is an important part of the cultural heritage and economy of Southeastern Massachusetts, yet water quality concerns and wetland protection laws challenge its commercial production. Here, we report inputs and outputs of water, nitrogen (N), and phosphorus (P) for a 2.12‐ha cranberry bed over a 2‐year period from 2013 to 2015. Water‐budget analysis indicated that precipitation contributed 40%, floodwater 37%, irrigation 15%, and groundwater 8% of water inputs to the cranberry bed. Minor annual variation in surface water discharge (~90 mm·year^?1 or 3%) contrasted with large decreases in net (= outputs ? inputs) nutrient export, from 16.2 to 9.1 kg N·ha^?1·year^?1 for total (dissolved + suspended particulate) nitrogen (TN) and from 3.34 to 1.47 kg P·ha^?1·year^?1 for total phosphorus (TP) between Years 1 and 2. Annual variation in net TN and TP export was tied to decreases in spring and summer nutrient export and controlled by the combined effects of fertilizer management, soil biogeochemistry, and hydrology. The relatively high spring TN export in Year 1 was associated with coincident increases in soil temperature and rainfall. A second factor was the timing of fertilizer application, which occurred 1 day prior to a major summer storm (i.e., third largest daily rainfall since 1926) and was responsible for up to 15% and 9% of the Year 1 TN and TP export, respectively. Nutrient budgets, which balanced water and fertilizer inputs with water, fruit, and vegetative outputs, were consistent with the burial of 21.6 kg N·ha^?1·year^?1 and 7.27 kg P·ha^?1·year^?1. Field measurements indicated that burial would increase TN and TP in the shallow (0–5 cm) rooting zone by 14% and 6%, respectively, which seemed plausible based on the relatively young age of the bed (4–5 years) and new root growth patterns in Vaccinium plants.     

Assessment of small-diameter shallow wells for managed aquifer recharge at a site in southern Styria,Austria

An approach to establish the recharge component of managed aquifer recharge (MAR) has recently been proposed that uses small-diameter shallow wells installed using relatively inexpensive drilling methods such as direct push. As part of further development of that approach, a generalized procedure is presented for a technical and economic assessment of the approach’s potential in comparison to other systems. Following this procedure, the use of small-diameter wells was evaluated both experimentally and numerically for a site located in southern Styria, Austria. MAR is currently done at the site using a horizontal pipe infiltration system, and system expansion has been proposed with a target rate of 12 l/s using small-diameter wells as one possible option. A short-duration single-well field recharge experiment (recharge rate 1.3–3.5 l/s) was performed (recharge by gravity only). Numerical modeling of the injection test was used to estimate hydraulic conductivity (K). Quasi-steady-state, single-well recharge simulations for different locations, as well as a long-term transient simulation, were performed using the K value calibrated from the field injection test. Results indicate that a recharge capacity of 4.1 l/s was achievable with a maximum head rise of 0.2 m at the injection well. Finally, simulations were performed for three different well fields (4, 6 and 8 wells, respectively) designed to infiltrate a target rate of 12 l/s. The experimental and numerical assessments, supported by a cost analysis of the small-diameter wells, indicate that the small-diameter wells are a viable, cost-effective recharge approach at this and other similar sites.     

Tectonothermal history of the basement rocks in the western zone of the North China Craton and its tectonic implications

The basement of the North China Craton can be divided into the eastern, central and western zones, based on lithological, structural, metamorphic and geochronological data. The western zone comprises two different petrotectonic units: Archaean tonalitic–trondhjemitic–granodioritic (TTG) grey gneisses and metamorphic mafic rocks, and Palaeoproterozoic khondalite series. The former is characterized by isobaric cooling (IBC)-type anticlockwise P–T paths in the north-northwestern part of the zone and near-isothermal decompression (ITD)-type clockwise P–T paths in the eastern part, adjacent to the central zone. On the other hand, the tectonothermal evolution of Palaeoproterozoic khondalite series rocks is characterized exclusively by nearly isothermal decompression following the peak of metamorphism and then cooling, defining clockwise P–T paths. The Archaean TTG gneisses and associated mafic rocks with anticlockwise metamorphic P–T paths reflects an origin related to underplating and intrusion of mantle-derived magmas which may be derived from mantle plumes. They represent a late Archaean continental block in the western part of the North China Craton. The Palaeoproterozoic khondalite series rocks represent passive continental margin deposits. They were metamorphosed and deformed in the late Palaeoproterozoic during the amalgamation of the western continental block with another continental block in the east part of the North China Craton. The ITD-type clockwise P–T–t paths of the Palaeoproterozoic khondalite series rocks record the tectonothermal histories of the collision of the western and eastern continental blocks which resulted in the final assembly of the North China Craton at c. 1800 Ma.     

Thermo-tectonic history of Ryoke Basement in Hohi volcanic zone, northeast Kyushu, Japan: Constraints from fission track thermochronology

Abstract Apatite and zircon fission track ages from Ryoke Belt basement in northeast Kyushu show late Cretaceous, middle to late Eocene, middle Miocene and Quaternary groupings. The basement cooled through 240 ± 25°C, the closure temperature for fission tracks in zircon, mainly during the interval 74-90 Ma as a result of uplift and denudation, the pattern being uniform across northeast Kyushu. In combination with published K-Ar ages and the Turonian-Santonian age of sedimentation in the Onogawa Basin, active suturing along the Median Tectonic Line from 100-80 Ma, at least, is inferred. Ryoke Belt rocks along the northern margin of Hohi volcanic zone (HVZ) cooled rapidly through ∼100°C to less than 50°C during the middle Eocene to Oligocene, associated with 2.5-3.5 km of denudation. The timing of this cooling follows peak heating in the Eocene-Oligocene part (Murotohanto subbelt) of the Shimanto Belt in Muroto Peninsula (Shikoku) inferred previously, and coincides with the 43 Ma change in convergence direction of the Pacific-Eurasian plate and the demise of the Kula-Pacific spreading centre. Ryoke Belt rocks along the southern margin of HVZ have weighted mean apatite fission track ages of 15.3 ± 3.1 Ma. These reset ages are attributed to an increase in geothermal gradient in the middle Miocene combined with rapid denudation and uplift of at least 1.4 km. These ages indicate that heating of the overriding plate associated with the middle Miocene start of subduction of hot Shikoku Basin lithosphere extended into the Ryoke Belt in northeast Kyushu. Pleistocene apatite fission track ages from Ryoke Belt granites at depth in the centre of HVZ are due to modern annealing in a geothermal environment.     

Argo floats revealing bimodality of large-scale mid-depth circulation in the North Atlantic

Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.     

Emplacement mechanisms of the South Kona slide complex,Hawaii Island: sampling and observations by remotely operated vehicle Kaiko

Emplacement of a giant submarine slide complex, offshore of South Kona, Hawaii Island, was investigated in 2001 by visual observation and in-situ sampling on the bench scarp and a megablock, during two dives utilizing the Remotely Operated Vehicle (ROV) Kaiko and its mother ship R/V Kairei. Topography of the bench scarp and megablocks were defined in 3-D perspective, using high-resolution digital bathymetric data acquired during the cruise. Compositions of 34 rock samples provide constraints on the landslide source regions and emplacement mechanisms. The bench scarp consists mainly of highly fractured, vesiculated, and oxidized aa lavas that slumped from the subaerial flank of ancestral Mauna Loa. The megablock contains three units: block facies, matrix facies, and draped sediment. The block facies contains hyaloclastite interbedded with massive lava, which slid from the shallow submarine flank of ancestral Mauna Loa, as indicated by glassy groundmass of the hyaloclastite, low oxidation state, and low sulfur content. The matrix facies, which directly overlies the block facies and is similar to a lahar deposit, is thought to have been deposited from the water column immediately after the South Kona slide event. The draped sediment is a thin high-density turbidite layer that may be a distal facies of the Alika-2 debris-avalanche deposit; its composition overlaps with rocks from subaerial Mauna Loa. The deposits generated by the South Kona slide vary from debris avalanche deposit to turbidite. Spatial distribution of the deposits is consistent with deposits related to large landslides adjacent to other Hawaiian volcanoes and the Canary Islands.     

Landscape for change? International climate policy and energy transitions: evidence from sub-Saharan Africa

What is the role of the climate regime in facilitating rapid decarbonization of the world’s energy systems? We examine how core assumptions concerning the roles of the nation state, carbon markets and finance and technology in international climate policy are being challenged by the realities of how transitions in the energy systems are unfolding. Drawing on the critical region of sub-Saharan Africa, we examine the potential for international climate policy to foster new trajectories towards decarbonization.

Policy relevance

The international regime for climate policy has been in place for some twenty years. Despite significant changes in the landscape of energy systems and drivers of global GHG emissions over this time, the core principles and tools remain relatively stable – national governments, carbon markets, project-based climate finance and the transfer of technological hardware. Given the diversity of actors and drivers and the limited direct reach and influence of international climate policy, however, there is an urgent need to consider how the climate regime can best support the embryonic transitions that are slowly taking form around the world. To do this effectively requires a more nuanced understanding of the role of the state in governing these transitions beyond the notion of a cohesive state serving as rule-enforcer and transition manager. It also requires a broader view of technology, not just as hardware that is transferred, but as a set of practices and networks of expertise and enabling actors. Likewise, though markets have an important role to play as vehicles for achieving broader ends, they are not an end in themselves. Finally on finance, while acknowledging the important role of climate aid, often as a multiplier or facilitator of more ambitious private flows, it is critical to differentiate between the types of finance required for different transitions, many of which will not be counted under, or directed by, the climate regime. In sum, the (low-) carbon economy is being built in ways and in numerous sites that the climate regime needs to be cognizant of and engage with productively, and this may require fundamental reconsideration of the building blocks of the international climate regime.