Volume 4 Issue 1, January 2011

Ocean drilling is the most successful long-standing international collaboration in the geosciences. The invaluable archive of samples and data that has been built underpins our understanding of the Earth, its surface environment and climate. Planning the next phase is at an advanced stage.

Unusual wind patterns and the albedo feedback effect played crucial roles in the rapid reduction of Arctic sea-ice cover in recent years. Evidence is now building that a warmer ocean has also contributed to the thinning of Arctic ice.

The timing and origins of Alpine gorge formation are controversial. A high-resolution analysis of the inner gorges of the Swiss Alps suggests that these landforms were carved over successive interglacial periods, and survived the intervening glaciations.

The existence of a microbial community in the ocean crust has long been hypothesized. Isotopic evidence indicates that a deep biosphere of microbes both scrubs oceanic fluids of organic matter and produces new, yet old, organic carbon in situ.

Magma from the mantle meets the ocean at seafloor spreading centres. At young rifts, basalt sills may heat overlying sediments and induce natural carbon release; basalt flows elsewhere may offer secure reservoirs for sequestration of anthropogenic carbon.

Climate models suggest that deficits in soil moisture can lead to more frequent and severe hot summer temperatures. Observations confirm this effect, but only for relatively dry regions, where evaporation is limited by available moisture.

Bromine facilitates the oxidation of elemental mercury in the lower atmosphere in polar and subpolar regions. Measurements over the Dead Sea suggest that bromine also generates large quantities of oxidized mercury in the mid-latitudes.

Modelling studies have postulated a possible impact of soil-moisture deficit and drought on hot extremes. An analysis of observational indices from central and southeastern Europe confirms that summer hot extremes are linked to soil-moisture deficits in southeastern Europe but does not detect a similar effect in central Europe.

In the polar atmosphere, non-reactive gaseous elemental mercury is converted to a highly reactive form of mercury by halogens such as bromine. Measurements over the Dead Sea suggest that bromine also triggers reactive mercury formation over the mid-latitude ocean.

Climate change has increased the area affected by forest fires in boreal North America. An analysis of the depth of burning in forests and peatlands in Alaska indicates that ground-layer combustion has accelerated regional carbon losses.

Hydrothermal fluids circulate through the upper portion of the oceanic crust. Isotopic analyses suggest that chemosynthetic microbial communities in the crust synthesize dissolved organic carbon in hydrothermal ridge-flank fluids.

Marine sediments contain large quantities of carbon, primarily in the form of gas hydrate. Isotopic analyses suggest that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon in sea water overlying hydrate-bearing seeps in the northeastern Pacific Ocean.

The tropical African rainbelt is an important component of atmospheric circulation and the global hydrological cycle. Reconstructions of vegetation in tropical Africa over the past 23,000 years suggest that the rainbelt expanded and contracted in response to changes in high-latitude climate conditions.

During the last deglaciation, climate changes over Greenland and Antarctica on millennial timescales were asynchronous. A temperature record from the Talos Dome in Antarctica confirms this asynchrony and shows clear regional differences in deglacial warming between the Indo-Pacific and Atlantic sectors of Antarctica.

Continental rifting creates narrow ocean basins, where coastal ocean upwelling and enhanced silicate weathering remove carbon dioxide from the atmosphere. Evidence from seismic data, sonar backscatter and seafloor images, and geochemical water analyses suggest that in young sedimented rifts, active magmatism occurs in a broader region than appreciated and releases carbon from the sediments.

Deformation in the crust and mantle — measured using seismic anisotropy — is poorly constrained in the western United States because of inconsistencies in the existing data. A three-dimensional model that reconciles these discrepancies reveals that seismic anisotropy in the crust correlates with different geological provinces, but is unrelated to anisotropy in the underlying mantle.

The origins of Alpine valleys are controversial. Topographic data from the Swiss Alps suggest that the valleys have been incised progressively during consecutive glacial–interglacial cycles.

Massimo Frezzotti and colleagues saw their 17-ton vehicle drop 10 m into an ice crevasse in their quest to recover the climatic history of East Antarctica.

Deep-sea carbon cycling is poorly constrained, not least because this remote environment is so difficult to explore. In this web focus we highlight the prevalence and diversity of seabed carbon sources.