Marine ecosystems are centrally important to the biology of the planet, yet a comprehensive understanding of how anthropogenic climate change is affecting them has been poorly developed. Recent studies indicate that rapidly rising greenhouse gas concentrations are driving ocean systems toward conditions not seen for millions of years, with an associated risk of fundamental and irreversible ecological transformation. The impacts of anthropogenic climate change so far include decreased ocean productivity, altered food web dynamics, reduced abundance of habitat-forming species, shifting species distributions, and a greater incidence of disease. Although there is considerable uncertainty about the spatial and temporal details, climate change is clearly and fundamentally altering ocean ecosystems. Further change will continue to create enormous challenges and costs for societies worldwide, particularly those in developing countries.

http://science.sciencemag.org/content/sci/328/5985/1523.full.pdf

The impact of climate change on the world's marine ecosystems.

The cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease. Altitude-dependent scaling factors are required to compensate for this effect in calculating cosmic ray exposure ages. Scaling factors in current use assume a uniform relationship between altitude and atmospheric pressure over the Earth's surface. This masks regional differences in mean annual pressure and spatial variation in cosmogenic isotope production rates. Outside Antarctica, air pressures over land depart from the standard atmosphere by ±4.4 hPa (1σ) near sea level, corresponding to offsets of ±3–4% in isotope production rates. Greater offsets occur in regions of persistent high and low pressure such as Siberia and Iceland, where conventional scaling factors predict production rates in error by ±10%. The largest deviations occur over Antarctica where ground level pressures are 20–40 hPa lower than the standard atmosphere at all altitudes. Isotope production rates in Antarctica are therefore 25–30% higher than values calculated by scaling Northern Hemisphere production rates with conventional scaling factors. Exposure ages of old Antarctic surfaces, especially those based on cosmogenic radionuclides at levels close to saturation, may be millions of years younger than published estimates.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2000JB900181

Air pressure and cosmogenic isotope production

Global cooling in the Cenozoic, which led to the growth of large continental ice sheets in both hemispheres, may have been caused by the uplift of the Tibetan plateau and the positive feedbacks initiated by this event. In particular, tectonically driven increases in chemical weathering may have resulted in a decrease of atmospheric C02 concentration over the past 40 Myr.

Tectonic forcing of late Cenozoic climate

An Astronomically Tuned Neogene Time Scale (ATNTS2012) is presented, as an update of ATNTS2004 in GTS2004. The new scale is not fundamentally different from its predecessor and the numerical ages are identical or almost so. Astronomical tuning has in principle the potential of generating a stable Neogene time scale as a function of the accuracy of the La2004 astronomical solution used for both scales. Minor problems remain in the tuning of the Lower Miocene. In GTS2012 we will summarize what has been modified or added since the publication of ATNTS2004 for incorporation in its successor, ATNTS2012. Mammal biostratigraphy and its chronology are elaborated, and the regional Neogene stages of the Paratethys and New Zealand are briefy discussed. To keep changes to ATNTS2004 transparent we maintain its subdivision into headings as much as possible.

The Neogene Period

Polar temperatures over the last several million years have, at times, been slightly warmer than today, yet global mean sea level has been 6-9 metres higher as recently as the Last Interglacial (130,000 to 115,000 years ago) and possibly higher during the Pliocene epoch (about three million years ago). In both cases the Antarctic ice sheet has been implicated as the primary contributor, hinting at its future vulnerability. Here we use a model coupling ice sheet and climate dynamics-including previously underappreciated processes linking atmospheric warming with hydrofracturing of buttressing ice shelves and structural collapse of marine-terminating ice cliffs-that is calibrated against Pliocene and Last Interglacial sea-level estimates and applied to future greenhouse gas emission scenarios. Antarctica has the potential to contribute more than a metre of sea-level rise by 2100 and more than 15 metres by 2500, if emissions continue unabated. In this case atmospheric warming will soon become the dominant driver of ice loss, but prolonged ocean warming will delay its recovery for thousands of years.

Contribution of Antarctica to past and future sea-level rise

Eocene–Oligocene paleoecology and the diatom genus Kisseleviella Sheshukova-Poretskaya from the Victoria Land Basin, Antarctica

Silicoflagellates are usually associated with simple skeletons made of a domal latticework of rod-shaped elements, known as the apical structure, which is attached to a polygonal basal ring. Silicoflagellate reproduction is poorly understood (Moestrup & Thomsen, 1990) but they are known to divide mitotically associated with the construction of a double skeleton. Such double skeletons connected at the abapical face of the basal ring are observed from Recent and fossil material. Double skeletons of Dictyocha and Distephanus noted in Cenozoic sediments (Dumitricǎ, 1973, pl. 4, fig. 8; Boney, 1976) show basal rings positioned with their corners in close proximity. Ling & Takahashi (1985, pl. 1, fig. 5) and Takahashi et al . (2009, pl. 2, figs 3, 5) illustrate Distephanus with the spines of the two skeletons in exact alignment with one another.

Recent work in a Campanian sequence of strata near Horton River, District of Mackenzie in the Northwest Territories, Canada …

https://jm.copernicus.org/articles/29/185/2010/jm-29-185-2010.pdf

A rare double skeleton of the silicoflagellate Corbisema

Glacial erratics of Eocene sediments at McMurdo Sound, Antarctica, contain plant microfossils. These include Araucaria leaves, at least two species of Nothofagus based on leaves, and three types of non-Nothofagus dicotyledonous leaves. One of the Nothofagus species has plicate vernation and was therefore deciduous. Two types of Nothofagus fruits are present, two-flanged and three-flanged. The three-flanged fruits indicate that they came from a four-valved cupule and thus from one of the (currently) temperate subgenera.Copyright 2000 by the American Geophysical Union

Eocene plant macrofossils from erratics, McMurdo Sound, Antartica

1Istituto Nazionale di Geofisica e Vulcanologia, Via di Vigna Murata, 605, I-00143 Rome Italy 2ANDRILL Science Management Office, University of Nebraska-Lincoln, , Lincoln, NE 68588 – USA 3Department of Geosciences, Univ. of Nebraska-Lincoln, Lincoln, NE 68588-0341 USA 4Dipartimento di Scienze della Terra, Università di Siena, Via del Laterino 8, I-53100 Siena Italy 5http://www.andrill.org/projects/sms/team.html

/pdf/background-to-the-andrill-southern-mcmurdo-sound-project-1ghjtzrakq.pdf

David M. Harwood

Papers

Eocene–Oligocene paleoecology and the diatom genus Kisseleviella Sheshukova-Poretskaya from the Victoria Land Basin, Antarctica

A rare double skeleton of the silicoflagellate Corbisema

Eocene plant macrofossils from erratics, McMurdo Sound, Antartica

Background to the ANDRILL Southern McMurdo Sound Project, Antarctica

Introduction to 'long-term changes in Southern high-latitude ice sheets and climate, the Cenozoic history'