Based on the multidecadal component of a Fram Strait Sea Ice Export reconstruction and on a sea surface temperature proxy for changes in the ocean circulation, we construct a bifurcation diagram for two cycles of the Atlantic Multidecadal Oscillation. It suggests a hysteresis behavior that is consistent with non-linear convective adjustment to changes in deep water formation in the North Atlantic and with the meridional overturning circulation bistability

Through its nonlinear dynamics and involvement in past abrupt climate shifts the thermohaline circulation (THC) represents a key element for the understanding of rapid climate changes. The expected THC weakening under global warming is characterized by large uncertainties, and it is therefore of significant importance to identify ocean circulation changes over the last century. By applying various statistical techniques on two global sea surface

Instrumental climate observations provide robust records of global land and ocean temperatures during the twentieth century. Unlike for temperature, continuous salinity observations in the surface ocean are scarce prior to 1970, and the magnitude of salinity changes during the twentieth century is largely unknown. Surface ocean salinity is a major component in climate dynamics, as it influences ocean circulation and water mass formation. Here we

Dansgaard-Oeschger and Heinrich events are the most pronounced climate changes over the last 120,000 years. Although many of their properties were derived from climate reconstructions, the associated physical mechanisms are not yet fully understood. These events are paced by a ~1500 year periodicity whose origin remains unclear. In a conceptual model approach, we show that this millennial variability can originate from rectification of an external

The role of anomalous Indian Ocean sea surface temperature (SST) in forcing east African rainfall anomalies during December-January 1997/98 has been investigated by means of atmospheric model response experiments. It is shown that the strong precipitation anomalies that led to severe flooding over eastern equatorial Africa can be directly related to the contemporaneous changes in the Indian Ocean's SST. The authors' set of ensemble experiments prescribing

Recent studies suggest that interannual, decadal and quasibidecadal periodicities dominate global sea surface temperature and sea level pressure variability over past hundred years. In this study, we present evidence that the quasibidecadal mode of variability can be considered in a first order approximation as resulting from a linear combination between the dominant modes of variability in the Tropical Pacific (associated with interannual variability).

Observational data are used to emphasize a 5- to 7-yr lag between the main modes of variability in the midlatitudes and in the Tropics. Considering this finding a mechanism for quasidecadal variability based on Tropics-midlatitudes and ocean-atmosphere interaction is described. It appears that the signal associated with the SST anomalies in the northern region of the tropical Atlantic is transferred in midlatitudes through the atmosphere and it will

Based on analysis of observational data we show that the impact of the North Atlantic Oscillation (NAO) and El Nino-Southern Oscillation (ENSO) on the Danube river flow variability shows important decadal variations. A lag-correlation analysis reveals that winter SST from tropical Pacific and some regions from the North Atlantic are significantly correlated with the streamflow variations from spring and summer suggesting a possible predictive skill

We investigate the structure of the Northern Hemisphere atmospheric circulation anomaly patterns associated with the dominant mode of interannual variability in the Tropical Pacific and the dominant mode of quai-decadal variability in the Atlantic basin. There is evidence that the superposition of the atmospheric patterns associated with these modes possesses an Arctic Oscillation -like structure. We suggest that part of the Arctic Oscillation variability

The decadal variability (>5 years) of the Danube river flow in the lower basin and its connection with the North Atlantic Oscillation (NAO) is analysed for the period 1931-95. Associated linkages with precipitation (PP) in the European sector, global sea surface temperature (SST) and atmospheric circulation for the period 1931-81, and the 500 hPa geopotential heights (G500) over the Northern Hemisphere for the period 1948-95 are also investigated.