Jerónimo López-Martínez

Circum-Antarctic Coastal Environmental Shifts During the Late Quaternary Reflected by Emerged Marine Deposits

This review assesses the circumpolar occurrence of emerged marine macrofossils and sediments from Antarctic coastal areas in relation to Late Quaternary climate changes. Radiocarbon ages of the macrofossils, which are interpreted in view of the complexities of the Antarctic marine radiocarbon reservoir and resolution of this dating technique, show a bimodal distribution. The data indicate that marine species inhabited coastal environments from at least 35 000 to 20 000 yr BP, during Marine Isotope Stage 3 when extensive iceberg calving created a ‘meltwater lid’ over the Southern Ocean. The general absence of these marine species from 20 000 to 8500 yr BP coincides with the subsequent advance of the Antarctic ice sheets during the Last Glacial Maximum. Synchronous re-appearance of the Antarctic marine fossils in emerged beaches around the continent, all of which have Holocene marine-limit elevations an order of magnitude lower than those in the Arctic, reflect minimal isostatic rebound as relative sea-level rise decelerated. Antarctic coastal marine habitat changes around the continent also coincided with increasing sea-ice extent and outlet glacial advances during the mid-Holocene. In view of the diverse environmental changes that occurred around the Earth during this period, it is suggested that Antarctic coastal areas were responding to a mid-Holocene climatic shift associated with the hydrological cycle. This synthesis of Late Quaternary emerged marine deposits demonstrates the application of evaluating circum-Antarctic phenomena from the glacial-terrestrial-marine transition zone.

The Balearic Promontory geomorphology (western Mediterranean): morphostructure and active processes

In this paper, a detailed study of the submarine geomorphology surrounding the Balearic Promontory (western Mediterranean), a northeast prolongation of the Neogene Betic Range in southern Spain, is presented from a series of high-resolution tools including swath bathymetry and seismic reflection profiling. The study identifies the main features of the continental shelf, slope and basins surrounding the Balearic Islands. We show a variety of seafloor relief that owes its origin to several geologic processes, which ultimately control the transport of sediment from the shallower areas to the deep basin. The most important processes are erosion of the shelf and upper slope (terraces associated with different Quaternary sea-level stands and canyons), transport and sediment deposition in the lower slope and base-of-slope by turbidity currents, volcanism and instability processes (landslides scarps and debris lobes). The swath data show that tectonics plays an important role in shaping the submarine slopes of Eivissa and Formentera, the two southernmost islands, as well as its interplay with sedimentary processes, especially mass wasting. Finally, several areas show evidence of pockmarks, which indicate that fluid migration take place in the sediments, probably conditioning several other processes such as mass wasting.

Bransfield Basin, Antarctic Peninsula: Not a normal backarc basin

The Bransfield Basin, a marginal basin located northwest of the Antarctic Peninsula, has been habitually considered as a backarc basin associated with the rollback process that took place along an inactive plate boundary, the South Shetland Trench, where the Antarctic and the Phoenix plates meet. New geophysical and structural data discussed in this paper show that the basin opening is related to a sinistral simple-shear couple between the Scotia and the Antarctic plates, and not to the previously suggested rollback mechanism. The widening of the Bransfield Basin and the lack of trench retreat are causing compression in the South Shetland Islands. Two different neotectonic stress directions, with interchanged stress axes, are found in the area of the South Shetland block.

A roadmap for Antarctic and Southern Ocean science for the next two decades and beyond

Abstract Antarctic and Southern Ocean science is vital to understanding natural variability, the processes that govern global change and the role of humans in the Earth and climate system. The potential for new knowledge to be gained from future Antarctic science is substantial. Therefore, the international Antarctic community came together to ‘scan the horizon’ to identify the highest priority scientific questions that researchers should aspire to answer in the next two decades and beyond. Wide consultation was a fundamental principle for the development of a collective, international view of the most important future directions in Antarctic science. From the many possibilities, the horizon scan identified 80 key scientific questions through structured debate, discussion, revision and voting. Questions were clustered into seven topics: i) Antarctic atmosphere and global connections, ii) Southern Ocean and sea ice in a warming world, iii) ice sheet and sea level, iv) the dynamic Earth, v) life on the precipice, vi) near-Earth space and beyond, and vii) human presence in Antarctica. Answering the questions identified by the horizon scan will require innovative experimental designs, novel applications of technology, invention of next-generation field and laboratory approaches, and expanded observing systems and networks. Unbiased, non-contaminating procedures will be required to retrieve the requisite air, biota, sediment, rock, ice and water samples. Sustained year-round access to Antarctica and the Southern Ocean will be essential to increase winter-time measurements. Improved models are needed that represent Antarctica and the Southern Ocean in the Earth System, and provide predictions at spatial and temporal resolutions useful for decision making. A co-ordinated portfolio of cross-disciplinary science, based on new models of international collaboration, will be essential as no scientist, programme or nation can realize these aspirations alone.

Rock glaciers in the South Shetland Islands, Western Antarctica

Rock glaciers are found in the peripheral regions of Antarctica particularly in the Antarctic Peninsula region. Study of these features is relevant for the palaeoenvironmental reconstruction of maritime Antarctica because they are indicators of permafrost and periglacial conditions. This paper reports and analyzes the results of an inventory of rock glaciers and protalus lobes in the South Shetland Islands. Nine rock glaciers and eleven protalus lobes have been identified. All of them are located in recently deglaciated zones between 300 m a.s.l. and sea level and they cover an area of 497×103 m2. Tongue-shaped rock glaciers are more common than lobate types, being in general of medium and small sizes. They are talus rock glaciers (55%) and debris rock glaciers (45%), according to the genetic classification. The lack of a preferred orientation suggests that there is no significant microclimate control on their distribution. They are related to particular morphodynamic situations. Estimated annual velocities, based on relationships with raised beaches and transported debris volumes, range between 2.4 and 97 cm year−1, within the ranges reported for other rock glaciers. Three groups of rock glaciers can be recognised: (a) those immediate postdating the last major ice recession, (b) rock glaciers younger than 2000 years BP but pre-dating the Little Ice Age (LIA), and (c) rock glaciers formed during the LIA.

The scope of science for the International Polar Year, 2007-2008

Produced by the ICSU/WMO Joint Committee for IPY 2007–2008 By: Ian Allison and Michel Beland (Co-Chairs), Keith Alverson, Robin Bell, David Carlson, Kjell Danell, Cynan Ellis-Evans, Eberhard Fahrbach, Edith Fanta, Yoshiyuki Fujii, Gisbert Gilbertson, Leah Goldfarb, Grete Hovelsrud-Broda, Johannes Huber, Vladimir Kotlyakov, Igor Krupnik, Jeronimo Lopez-Martinez, Tillmann Mohr, Dahe Qin, Volker Rachold, Chris Rapley, Odd Rogne, Eduard Sarukhanian, Colin Summerhayes, Cunde Xiao

Presence of endocrine disruptors in freshwater in the northern Antarctic Peninsula region

The increasing human presence in Antarctica and the waste it generates is causing an impact on the environment at local and border scale. The main sources of anthropic pollution have a mainly local effect, and include the burning of fossil fuels, waste incineration, accidental spillage and wastewater effluents, even when treated. The aim of this work is to determine the presence and origin of 30 substances of anthropogenic origin considered to be, or suspected of being, endocrine disruptors in the continental waters of the Antarctic Peninsula region. We also studied a group of toxic metals, metalloids and other elements with possible endocrine activity. Ten water samples were analyzed from a wide range of sources, including streams, ponds, glacier drain, and an urban wastewater discharge into the sea. Surprisingly, the concentrations detected are generally similar to those found in other studies on continental waters in other parts of the world. The highest concentrations of micropollutants found correspond to the group of organophosphate flame retardants (19.60-9209ngL(-1)) and alkylphenols (1.14-7225ngL(-1)); and among toxic elements the presence of aluminum (a possible hormonal modifier) (1.7-127µgL(-1)) is significant. The concentrations detected are very low and insufficient to cause acute or subacute toxicity in aquatic organisms. However, little is known as yet of the potential sublethal and chronic effects of this type of pollutants and their capacity for bioaccumulation. These results point to the need for an ongoing system of environmental monitoring of these substances in Antarctic continental waters, and the advisability of regulating at least the most environmentally hazardous of these in the Antarctic legislation.

Recent tectonic and morphostructural evolution of Byers Peninsula (Antarctica): insight into the development of the South Shetland Islands and Bransfield Basin

Byers Peninsula forms the western extremity of the Livingston Island (Antarctica) in the continental South Shetland Block. This tectonic block is bounded by the South Shetland Trench to the north, the Bransfield back-arc basin to the south, and extends to the South Scotia Ridge on the east. Westwards it is connected to the Antarctic Plate by a broad deformation zone located at the southern end of the Hero Fracture Zone. In Byers Peninsula we analyzed more than 1,200 lineaments, and 359 fault planes from 16 sites, both in sedimentary and intrusive igneous rocks. Statistical analysis of lineaments and mesoscopic fractures, with a length varying between 31 and 1,555 m, shows a NW-SE maximum trend, with two NE-SW and ENE-WSW secondary maximums. Fault orientation analysis shows similar trends suggesting that most of the lineaments correspond to fractures. Due to the absence of striated faults and the lack of kinematic evidence on the regime in most of the analyzed faults we have used the Search Grid paleostress determination method. The results obtained allow us to improve and complete the data on the recent evolution of the South Shetland Block. In this complex geodynamic setting, Byers Peninsula has been subjected to NNW-SSE to NNE-SSW extension related to Bransfield Basin opening and NE-SW and NW-SE local compressions respectively associated to Scotia-Antarctic plate convergence and the South Shetland Trench subduction.

Active tectonics and morphostructure at the northern margin of central Bransfield Basin, Hurd Peninsula, Livingston Island (South Shetland Islands)

Geophysical, structural, geomorphological, topographical and bathymetric data from the Hurd Peninsula area, Livingston Island, South Shetland archipelago, suggest that an extensional fault system, orientated NW–SE, together with a conjugate group of NE–SW normal oblique-slip faults, control the landforms in this area. These structures separate fault-bounded blocks of different heights, giving rise to a horstgraben structure. The depressed blocks were filled by glaciers and flooded in part by the sea. The recent movement of these faults can be established from the calculated isopachs of a small Quaternary sedimentary basin, related to this extensional fault system, which shows that sedimentary bed thickness is controlled mainly by the NE–SW fault system. Geomorphological analysis also shows that the NW–SE faults control the main morphostructures of this region. The character of the recent stress tensor has been established from fault-slip data, taking into account only those faults that are related to morphostructures. The calculated palaeostress tensor is extensional, with a N46°E main extension direction, and an average stress ratio of 0.17.

Delivering 21st century Antarctic and Southern Ocean science

Abstract The Antarctic Roadmap Challenges (ARC) project identified critical requirements to deliver high priority Antarctic research in the 21st century. The ARC project addressed the challenges of enabling technologies, facilitating access, providing logistics and infrastructure, and capitalizing on international co-operation. Technological requirements include: i) innovative automated in situ observing systems, sensors and interoperable platforms (including power demands), ii) realistic and holistic numerical models, iii) enhanced remote sensing and sensors, iv) expanded sample collection and retrieval technologies, and v) greater cyber-infrastructure to process ‘big data’ collection, transmission and analyses while promoting data accessibility. These technologies must be widely available, performance and reliability must be improved and technologies used elsewhere must be applied to the Antarctic. Considerable Antarctic research is field-based, making access to vital geographical targets essential. Future research will require continent- and ocean-wide environmentally responsible access to coastal and interior Antarctica and the Southern Ocean. Year-round access is indispensable. The cost of future Antarctic science is great but there are opportunities for all to participate commensurate with national resources, expertise and interests. The scope of future Antarctic research will necessitate enhanced and inventive interdisciplinary and international collaborations. The full promise of Antarctic science will only be realized if nations act together.