Journal Review 11 – 17 June 2014 (Nature, Science, Geology)

NATURE

1. Acidic oceans shrink plankton

Nature 510, 190 (12 Jun 2014) doi: 10.1038/510190a

As oceans take up more carbon dioxide, their increasing acidity could be decreasing the weight of one of the most abundant calcium-producing marine phytoplankton. Meier et al. found Emiliania huxleyi to be decreasing in weight since 1993 and is now at its lowest value in the past 10 000 years.

2. Planetary science: Early planet helped make Moon

Nature 510, 190 (12 Jun 2014) doi: 10.1038/510190c

Small chemical differences between Earth and the Moon support the idea that the Moon formed from remnants of a large early planet, or protoplanet, that smashed into Earth 4.5 billion years ago. Herwartz et al. measured ¹⁷O in Earth rocks, meteorites and lunar samples and found 12ppm more ¹⁷O in Moon rocks than Earth samples. The impacting protoplanet could have been chemically similar enough to Earth, at least in terms of oxygen, that any imprint would have been difficult to detect.

3. Increased frequency of extreme Indian Ocean Dipole events due to greenhouse warming

Wenju Cai, Agus Santoso, Guojian Wang, Evan Weller, Lixin Wu, Karumuri Ashok, Yukio Masumoto & Toshio Yamagata

Nature 510, 254-258 (12 June 2014) doi: 10.1038/13327

Using climate models, the authors project that the frequency of extreme positive IOD events will increase by almost a factor of 3. They find that a mean state change, with weakening of both equatorial westerly winds and eastward oceanic currents in association with a faster warming in the western than the eastern equatorial Indian Ocean, facilitates more frequent occurrences of wind and oceanic current reversal. This leads to more frequent pIOD events.

SCIENCE

4. Evidence for mesothermy in dinosaurs

John M. Grady, Brian J. Enquist, Eva Dettweiler-Robinson, Natalie A. Wright, Felisa A. Smith

Vol. 344 no. 6189 pp. 1268-1272 doi:10.1126/science.1253143

Using a metabolic scaling approach, growth and metabolic rates of dinosaurs were found to follow theoretical predictions. Grady et al. conclude that the modern dichotomy of endothermic versus ectothermic is overly simplistic.

5. Carbon-mapping satellite will monitor plants’ faint glow

Eric Hand

Vol. 344 no. 6189 pp. 1211-1212 doi:10.1126/science.344.6189.1211

With the launch of NASA’s Orbiting Carbon Observatory-2 (OCO-2) in July, scientist will be able to look at chlorophyll fluorescence, which will allow them to understand photosynthesis in plants and amount of carbon plants take up.

6. Onset of Mediterranean outflow into the North Atlantic

F. Javier Hernandez-Molina, Dorrik A. V. Stow, Carlos A. Alvarez-Zarikian, Gary Acton, Andre Bahr et al.

Vol. 344 no. 6189 pp. 1244-1250 doi:10.1126/science.1251306

Sediments obtained along the southwestern Iberian margin during IODP Expedition 339 constrain Mediterranean Outflow Water circulation patterns from the Pliocene epoch to the present day. Depositional hiatuses coinciding with regional tectonic events and changes in global thermohaline circulation indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. These suggest MOW influences the AMOC, THC and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics.

GEOLOGY

7. The contribution of mountains to global denudation

Isaac J. Larsen, David R. Montgomery and Harvey M. Greenberg

v. 42 no. 6 p. 527-530

doi:10.1130/G35136.1

Larsen et al. use an empirical model to predict that more than 50% of the total denudation and 40% of chemical denudation occur on the steepest 10% of Earth’s terrestrial surface.

8. Chemical weathering under the Greenland Ice Sheet

Joseph A. Graly, Neil F. Humphrey, Claire M. Landowski and Joel T. Harper

v. 42 no. 6 p. 551-554

doi:10.1130/G35370.1

Borehole and outlet water samples were collected from multiple locations on a major land-terminating outlet of the Greenland Ice Sheet. The bulk chemical composition shows much less influence of sulphides and carbonates than found in alpine glaciers, suggesting the sediment under the ice sheet has become depleted of accessory minerals. The dissolved solid concentrations are comparable to and in some cases exceed those in alpine glaciers, suggesting large ice masses are capable of generating substantial dissolved loads through silicate weathering mechanisms.

9. Thick sediments beneath Greenland’s ablation zone and their potential role in future ice sheet dynamics

Fabian Walter, Julien Chaput and Martin P. Luthi

v. 42 no. 6 p. 487-490

doi:10.1130/G35492.1

Using receiver function modelling of teleseismic P-waves, a thick (at least 10s of meters) sediment layer beneath a site in Greenland’s ablation zone was discovered.

10. Expanded glaciers during a dry and cold Last Glacial Maximum in equatorial East Africa

Meredith A. Kelly, James M. Russell, Margaret B. Baber, Jennifer A. Howley, Shannon E. Loomis, Susan Zimmerman, Bob Nakileza and Joshua Lukaye

v. 42 no. 6 p. 512-522

doi:10.1130/G35421.1

The authors used ¹⁰Be surface exposure dating to determine ages of quartz-rich boulders atop moraines in the Rwenzori Mountains (on the border of Uganda and the Democratic Republic of Congo). The ages document expanded glaciers ca. 23.4 and 20.1 ka. Indicating that glaciers in equatorial East Africa advanced during the global Last Glacial Maximum under dry and cold conditions.