Volume 2 Issue 7, July 2009

The Netherlands has a long and varied history of coastal and river flood management. The anticipation of sea-level rise during the twenty-first century has renewed the push for sustainable solutions to coastal vulnerability.

Changes in continental water stores, largely human-induced, affect sea level. Better hydrological models and observations could clarify the land's role in sea-level variations.

Homer's Ithaca had been viewed as a work of poetic licence and imprecise geography. However, as recent research shows the island's form may have been disguised over the past two millennia by catastrophic rockfalls, co-seismic uplift events and relative sea-level change.

Ammonia is a significant atmospheric pollutant whose global distribution is poorly understood. Satellite measurements highlight ammonia hotspots across the globe and indicate that current inventories may underestimate emissions in the Northern Hemisphere.

It is unclear whether the modern processes of mercury cycling — such as mercury deposition in polar regions — operated before anthropogenic emissions. Ice-core records from Antarctica now reveal strikingly high mercury concentrations during the coldest glacial periods.

Seafloor vents spewing mineral-rich plumes of hydrothermal fluid — termed black smokers — can persist at mid-ocean ridges for decades or longer. Earthquake data indicate that ongoing magma injection may determine their locations.

Large and rapid global sea-level changes indicate that polar ice sheets may have ephemerally existed during the Cretaceous greenhouse climate. Two oxygen isotopic studies provide evidence for and against this conclusion.

Some components of the climate system continue to adjust long after atmospheric greenhouse-gas levels have stopped changing. A coupled climate–vegetation model shows that forests can be committed to die-back or expansion before change is observed.

Understanding millennial-scale climate variability provides context for present and future climate change. It now emerges that temperatures were spatially and seasonally more heterogeneous over the past 1,000 years than previously thought.

Global mean sea-level change has increased from a few centimetres per century over recent millennia to a few tens of centimetres per century in recent decades. A review of the latest work shows that global mean sea-level rise is unlikely to exceed one metre over the twenty-first century, but regional departures from this global mean could reach several decimetres.

Ammonia is a significant atmospheric pollutant, accelerating the formation of particulate matter and damaging aquatic and terrestrial ecosystems. Infrared measurements of ammonia concentrations, obtained by the IASI/MetOp satellite, suggest that ammonia emissions in the Northern Hemisphere have been markedly underestimated.

Some aspects of the Earth system—such as global mean temperatures, and sea-level rise due to thermal expansion or melting of large ice sheets—continue to respond to climate change long after the stabilization of radiative forcing. Simulations with a coupled climate–vegetation model show that similarly ecosystems may be committed to significant change after climate stabilization.

Global sea-level rise, reduced sediment supply and subsidence threaten the stability of the Mississippi Delta. Calculations of riverine sediment load and storage indicate that 10,000–13,500 km² of the delta could be submerged by AD 2100.

For the past few centuries, multidecadal climate variability in North Atlantic sea surface temperatures has been modulated by the Atlantic Multidecadal Oscillation (AMO). A coral-based temperature reconstruction reveals that the AMO is a transient climate feature that only became significant after AD 1730.

Marine-terminating outlet glaciers control the stability of ice sheets. Exposure ages and radiocarbon dates show that an Arctic outlet glacier of the Laurentide ice sheet rapidly retreated about 9,500 years ago, and imply strong feedbacks between bathymetry and ice movement.

Sea level has varied by over one hundred metres across glacial–interglacial cycles over the past 520,000 years. An extended sea-level reconstruction shows a strong coupling between these sea-level changes and Antarctic surface temperatures over the past five glacial cycles.

Over the past two decades, seasonal periods of rapid atmospheric mercury deposition over Antarctica have been described. Ice core records show that similar events have occurred during previous glacial periods, probably as a result of interactions between sea salts and mineral dust in the polar atmosphere.

The mechanisms for localization of black-smoker systems at mid-ocean ridges remain to be fully understood. Seismic data for a segment of the Juan de Fuca ridge with long-lived black-smoker vents reveal ongoing magma recharge into the crustal magma chamber, thereby providing an explanation for the localization.

The two main iron-bearing silicate phases in the mantle—ferroperovskite and ferropericlase—are expected to partition iron isotopes differently. Theoretical calculations suggest that the spin state of iron strongly influences the iron isotopic composition of ferropericlase, whereas the iron isotopic composition of ferroperovskite is almost independent of spin state.

Seasonal changes in tropical rainfall patterns are associated with changes in the position of the intertropical convergence zone. Microbiological, molecular and hydrogen isotopic evidence from island lake sediments shows that the Pacific intertropical convergence zone was south of its modern position by as much as 500 km during the Little Ice Age.

Hermann M. Fritz and colleagues travelled by cargo boat through the Ayeyarwady delta in Myanmar to document the damage after cyclone Nargis.

William Wilcock and a team of scientists and engineers drilled holes in the sea floor, and inadvertently provided a breeding ground for octopuses, in their attempt to understand deep-ocean hydrothermal venting.

Paolo Gabrielli and colleagues dug deeply — and extremely cautiously — into Antarctic ice, to see whether the poles acted as a sink for mercury in the geological past.

In their report published in 2007, the Intergovernmental Panel on Climate Change projected that sea level is likely to rise between 18 and 59 centimetres by 2100, threatening the homes and livelihoods of millions who live in low-lying and deltaic regions. This focus draws together studies of past and present sea-level change, and predictions for future fluctuations, as well as presenting insights into the challenges facing coastal communities.