Threatening scenarios of a breakdown of the Atlantic thermohaline circulation (Figure 1), a collapse of northern European agriculture and fisheries, and of glaciers advancing on Scandinavia and Scotland have captured the popular imagination in recent years, with a number of newspaper reports, magazine articles and television documentaries covering this topic with a widely varying degree of accu...

Caprella mutica (Crustacea, Amphipoda) has been widely introduced to non-native regions in the last 40 years. Its native habitat is sub-boreal northeast Asia, but in the Northern Hemisphere, it is now found on both coasts of North America, and North Atlantic coastlines of Europe. Direct sequencing of mitochondrial DNA (cytochrome c oxidase subunit I gene) was used to compare genetic variation i...

We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The ...

Variability of the tropical Western Hemisphere warm pool (WHWP) of water warmer than 28.58C, which extends seasonally over parts of the eastern North Pacific, the Gulf of Mexico, the Caribbean, and the western tropical North Atlantic (TNA), was previously studied by Wang and Enfield using the da Silva data from 1945–93. Using additional datasets of the NCEP–NCAR reanalysis field and the NCEP SS...

Late Holocene climate in western North America was punctuated by periods of extended aridity called megadroughts. These droughts have been linked to cool eastern tropical Pacific sea surface temperatures (SSTs). Here, we show both short-term and long-term climate variability over the last 1,500 y from annual band thickness and stable isotope speleothem data. Several megadroughts are evident, in...

Threatening scenarios of a breakdown of the Atlantic thermohaline circulation (Figure 1), a collapse of northern European agriculture and fisheries, and of glaciers advancing on Scandinavia and Scotland have captured the popular imagination in recent years, with a number of newspaper reports, magazine articles and television documentaries covering this topic with a widely varying degree of accu...

We investigate variability in the surface ocean carbonate ion concentration ([CO 3 ]) on the basis of a long control simulation with an Earth System Model. The simulation is run with a prescribed, pre-industrial atmospheric CO2 concentration for 1000 years, permitting investigation of natural [CO 3 ] variability on interannual to multi-decadal timescales. We find high interannual variability in...

The last deglaciation was marked by large, hemispheric, millennial-scale climate variations: the Bølling-Allerød and Younger Dryas periods in the north, and the Antarctic Cold Reversal in the south. A chronology from the high-accumulation Law Dome East Antarctic ice core constrains the relative timing of these two events and provides strong evidence that the cooling at the start of the Antarcti...

During northern warm seasons, the overhead sun moves northward across the equator to the Northern Hemisphere. Because of the decrease in the meridional thermal gradients, particularly in midlatitudes, the Northern Hemisphere summer circulation becomes less rigorous in its intensity. In spite of this seasonal change, certain circulation elements still distinctly stand out. As shown in Fig. 1a, t...

[1] Extensive modeling studies show that changes in the anthropogenic forcing due to increasing greenhouse gases might lead to a slowdown of the Atlantic meridional overturning circulation (AMOC) in the 21st century, but the AMOC weakening estimated in most previous modeling studies is in depth space. Using a coupled ocean atmosphere model (GFDL CM2.1), this paper shows that in density space, t...