Observations show predictive skill of the minimum sea ice extent (Min SIE) from late winter anomalous offshore ice drift along the Eurasian coastline, leading to local ice thickness anomalies at the onset of the melt season}a signal then amplified by the ice-albedo feedback. We assess whether the observed seasonal predictability of September sea ice extent (Sept SIE) from Fram Strait Ice Area Export (FSIAE; a proxy for Eurasian coastal divergence) is present in global climate model (GCM) large ensembles, namely the CESM2-LE, GISS-E2.1-G, FLOR-LE, CNRM-CM6-1, and CanESM5. All models show distinct periods where winter FSIAE anomalies are negatively correlated with the May sea ice thickness (May SIT) anomalies along the Eurasian coastline, and the following Sept Arctic SIE, as in observations. Counterintuitively, several models show occasional periods where winter FSIAE anomalies are positively correlated with the following Sept SIE anomalies when the mean ice thickness is large, or late in the simulation when the sea ice is thin, and/or when internal variability increases. More important, periods with weak correlation between winter FSIAE and the following Sept SIE dominate, suggesting that summer melt processes generally dominate over late-winter preconditioning and May SIT anomalies. In general, we find that the coupling between the winter FSIAE and ice thickness anomalies along the Eurasian coastline at the onset of the melt season is a ubiquitous feature of GCMs and that the relationship with the following Sept SIE is dependent on the mean Arctic sea ice thickness.

We study the temporal variability of the wintertime Labrador Sea ice area. The driving factors of these intraseasonal and interannual variations are related to large scale atmospheric variability and cyclone variability both of which can be characterized by the Arctic Oscillation (AO) index. We observe negative trends in the maximum sea-ice area over the past 40 years, and a positive correlation between the AO index and Labrador Sea ice area. Using satellite-derived daily ice area along with reanalysis-derived cyclones, turbulent flux, wind, humidity, air and sea temperature fields, we delve into the physical coupling mechanisms by which cyclones influence the position of the ice edge in the Labrador Sea throughout the winter.

Abstract Climate change will affect both the mean state and seasonality of marine physical and biogeochemical properties, with important implications for the oceanic sink of atmospheric CO2. Here, we investigate the seasonal cycle of the air‐sea exchange of CO2 and pCO2,sw (surface seawater pCO2) and their long term changes using the CMIP6 submission of the NASA‐GISS modelE (GISS‐E2.1‐G). In comparison to the CMIP5 submission (GISS‐E2‐R), we find that on the global scale, the seasonal cycles of the CO2 flux and NPP have improved, while the seasonal cycles of dissolved inorganic carbon (DIC), alkalinity, and macronutrients have deteriorated. Moreover, for all ocean biogeochemistry fields, changes in skill between E2.1‐G and E2‐R display large regional variability. For E2.1‐G, we find similar modeled and observed CO2 flux seasonal cycles in the subtropical gyres, where seasonal anomalies of pCO2,sw and the flux are temperature‐driven, and the Southern Ocean, where anomalies are DIC‐driven. Biases in these seasonal cycles are largest in the subpolar and equatorial regions, driven by a combination of biases in temperature, DIC, alkalinity, and wind speed. When comparing the historical simulation to a simulation with an idealized increase in atmospheric pCO2, we find that the seasonal amplitudes of the CO2 flux and pCO2,sw generally increase. These changes are produced by increases in the sensitivity of pCO2,sw to its respective drivers. These findings are consistent with the notion that the seasonality of pCO2,sw is expected to increase due to the increase of atmospheric pCO2, with changes in the seasonality of temperature, DIC, and alkalinity having secondary influences.

Baffin Bay exports Arctic Water to the North Atlantic while receiving northward flowing Atlantic Water. Warm Atlantic Water has impacted the retreat of tidewater glaciers draining the Greenland Ice Sheet. Periods of enhanced Atlantic Water transport into Baffin Bay have been observed, but the oceanic processes are still not fully explained. At the end of 2010 the net transport at Davis Strait, the southern gateway to Baffin Bay, reversed from southward to northward for a month, leading to significant northward oceanic heat transport into Baffin Bay. This was associated with an extreme high in the Greenland Blocking Index and a stormtrack path that shifted away from Baffin Bay. Thus fewer cyclones in the Irminger Sea resulted in less frequent northerly winds along the western coast of Greenland, allowing anomalous northward penetration of warm waters, reversing the volume and heat transport at Davis Strait.

In multimillennial global warming simulations with the GISS‐E2‐R climate model, we observe multicentennial shutdowns with restoration and fast overshooting in North Atlantic Deep Water production despite the absence of exogenous freshwater input. AMOC (Atlantic Meridional Overturning Circulation) cessation is associated with a sea surface salinity reduction, initiated by increases in precipitation over evaporation as the climate warms. These multicentury shutdowns are the direct result of cooling in the North Atlantic associated with an aerosol indirect effect on cloud cover. The local cooling reduces evaporation within the North Atlantic, while warming elsewhere provides moisture to maintain nearly unperturbed precipitation in this region. As global warming continues, warm temperature (low density) anomalies spread northward at depth in the North Atlantic eventually destabilizing the water column, even though precipitation input at the surface is initially unchanged. Internal ocean freshwater transports do not play an important role in initiating this behavior, as assumed by some standard metrics of AMOC stability. The importance of the aerosol indirect effect in these runs is due to its role in strengthening the sea surface temperature‐evaporation feedback; this suggests a renewed focus on surface flux observations to help assess overturning stability. The length of the AMOC reduction, and its rapid recovery, may be relevant to the onset and end of the Younger Dryas, which occurred within a warming climate during the last deglaciation.

Interannual variations of latent heat fluxes (LHF) and sensible heat fluxes (SHF) over the Mediterranean for the boreal winter season (DJF) show positive trends during 1958–2011. Using reanalysis and satellite-based products, the variability and trends in the heat fluxes are compared with variations in three atmospheric teleconnection patterns: the North Atlantic Oscillation (NAO), the pressure and position of the Azores High (AH), and the East Atlantic-West Russia teleconnection pattern (EAWR). Comparison of correlations between the heat fluxes and teleconnections, along with analysis of composites of surface temperature, humidity, and wind fields for different teleconnection states, demonstrates that the AH explains the heat flux changes more successfully than NAO and EAWR. Trends in pressure and longitude of the Azores High show a strengthening and an eastward shift. Variations of the Azores High occur along an axis defined by lower pressure and westward location at one extreme and higher pressure and eastward location at the other extreme. The shift of the AH from predominance of the low/west state to the high/east state induces trends in Mediterranean Sea surface winds, temperature, and moisture. These, combined with sea surface warming trends, produce trends in wintertime sensible and latent heat fluxes.

The generation of zonal and eddy available potential energy (G(z) and G(e)) as formulated by Lorenz are computed on a global-, daily-, and synoptic-scale basis to consider the contribution of each diabatic heating component separately and in combination. Using global, mostly satellite-derived datasets for the diabatic heating components and the temperature enables us to obtain G(z) and, especially, G(e) from observations for the first time and at higher temporal and spatial resolution than previously possible. The role of clouds in maintaining G is investigated.The global annual mean G(z) is 1.52 W m(-2). Values reach a minimum of 0.63 W m(-2) in the Northern Hemisphere during spring and a maximum of 2.27 W m(-2) in the Southern Hemisphere during winter. The largest contributors to G(z) are latent heating in the tropical upper troposphere, associated with the intertropical convergence zone in the summer hemisphere and surface sensible heat fluxes in the winter pole. Diabatic cooling by radiative fluxes (mostly longwave) generally destroys G(z).The value of G(e) is negative and is about an order of magnitude smaller than G(z), with a global annual mean of -0.29 W m(-2). However, the small value of G(e) results from the cancellation of the contributions from the individual diabatic heating terms, which are actually roughly similar in magnitude to their G(z) contributions.The results presented herein suggest that the large-scale dynamics of the atmosphere organize the spatial and temporal distribution of clouds and precipitation in such a way as to increase the energy available to drive the circulation, a kind of positive feedback.

We analyze daily wintertime cyclone variability in the central and eastern Mediterranean during 1958–2001 and identify four distinct “cyclone states,” corresponding to the presence or absence of cyclones in each basin. Each cyclone state is associated with wind flows that induce characteristic patterns of cooling via turbulent (sensible and latent) heat fluxes in the eastern Mediterranean basin and Aegean Sea. The relative frequency of occurrence of each state determines the heat loss from the Aegean Sea during that winter, with largest heat losses occurring when there is a storm in the eastern but not central Mediterranean (eNOTc) and the smallest occurring when there is a storm in the central but not eastern Mediterranean (cNOTe). Time series of daily cyclone states for each winter allow us to infer Aegean Sea cooling for winters prior to 1985, the earliest year for which we have daily heat flux observations. We show that cyclone states conducive to Aegean Sea convection occurred in 1991/1992 and 1992/1993, the winters during which deepwater formation was observed in the Aegean Sea, and also during the mid-1970s and the winters of 1963/1964 and 1968/1969. We find that the eNOTc cyclone state is anticorrelated with the North Atlantic Oscillation (NAO) prior to 1977/1978. After 1977/1978, the cNOTe state is anticorrelated with both the NAO and the North Caspian Pattern, showing that the area of influence of large-scale atmospheric teleconnections on regional cyclone activity shifted from the eastern to the central Mediterranean during the late 1970s. A trend toward more frequent occurrence of the positive phase of the NAO produced less frequent cNOTe states since the late 1970s, increasing the number of days with strong cooling of the Aegean Sea surface waters.

Hydrographic observations indicated a shift of the main deep water formation in the Mediterranean Sea from its usual location in the Adriatic Sea to the Aegean Sea during the late 1980s and early 1990s, during winters 1991/1992 and 1992/1993. This event is known as the Eastern Mediterranean Transient (EMT). We report here a connection between EMT and specific atmospheric conditions which created anomalously large buoyancy fluxes from the Aegean Sea during winters 1991/1992 and 1992/1993 (the “enhanced EMT winters”). We use newly available, state of the art datasets with high space and time resolution and show that atypical cyclonic activity in the central Mediterranean versus the eastern basin produced the enhanced atmospheric forcing which intensified the EMT. An abatement of the frequency of cyclones in the central Mediterranean during 1992/1993 drastically reduced the northward advection of warm air over the Aegean Sea compared to more typical years, while an increase in the frequency of cyclones in the eastern Mediterranean enhanced the southward advection of cold air over the Aegean Sea, especially during 1991/1992. These changes significantly increased buoyancy flux losses from the Aegean Sea during the enhanced EMT winters, intensifying deep water production.

For initial GEWEX Hydrometeorology Panel water and energy budget study results for the period of 1986–1995, see the article by J. Roads on page 6. For results from the evaluation of the water cycle by ERA-40 using observation constrained land models, see article by K. Trenberth et al. on page 8. Left panel shows zonal, seasonal average generation of available potential energy, and right panel shows eddy available potential energy. Both were determined from observation-based calculations of atmospheric heating/cooling by radiation, precipitation and surface fluxes. See article by W. Rossow et al. on page 3. The annual Joint Scientific Committee (JSC) meeting was held in Pune, India in March. It was a busy meeting including a joint International Geosphere-Biosphere Programme–JSC (World Climate Research Programme) meeting where areas of mutual interest and potential collaboration were discussed. It also was the first meeting with Ann Henderson-Sellers in place as the WCRP Director. Peter Lemke, the outgoing Chair was replaced by John Church. On behalf of GEWEX, I thank Peter for his leadership, keen interest and participation in many of the GEWEX activities including the Coordinated Enhanced Observing Period (CEOP). It is natural to expect changes with new leadership and this meeting was no exception. One immediate change is that the Coordinated Observation and Prediction of the Earth System has been absorbed as part of the WCRP Strategic Plan. However, many of the specific initiatives such as the WCRP Observation and Assimilation Panel and WCRP Modelling Panel will continue to perform their functions of coordination across the WCRP projects. The Pune meeting placed more focus on activities such as extremes, monsoons, and An-thropogenic Climate Change (ACC). All WCRP projects are asked to contribute to ACC studies. Specific to GEWEX and CEOP, a number of decisions and recommendations were provided at the meeting. Some of highlights, which will require serious discussion and attention are summarized below. The JSC expressed appreciation for the GEWEX roadmap which responds to WCRP's strategic framework ; a special subgroup was established to review the objectives, implementation, milestones, and timeline of our roadmap. We will work closely with Drs. T. as they undertake this review but will also proceed to refine and implement the actions in the roadmap. The JSC encouraged GEWEX to increase its contribution to predictability and prediction studies and to accelerate progress on studies related to the role of land-surface processes in predictability on intraseasonal, seasonal and …