Geophysical Fluid Dynamics Laboratory

About: Geophysical Fluid Dynamics Laboratory is a facility organization based out in Princeton, New Jersey, United States. It is known for research contribution in the topics: Climate model & Climate change. The organization has 525 authors who have published 2432 publications receiving 264545 citations. The organization is also known as: GFDL.

Multidecadal climate variability in the Greenland Sea and surrounding regions: A coupled model simulation

Abstract: Pronounced oscillations of ocean temperature and salinity occur in the Greenland Sea in a 2000 year integration of a coupled ocean-atmosphere model. The oscillations, involving both the surface and subsurface ocean layers, have a timescale of approximately 40-80 years, and are associated with fluctuations in the inten- sity of the East Greenland Current. The Greenland Sea temperature and salinity variations are preceded by large-scale changes in near-surface salinity in the Arctic, which appear to propagate out of the Arctic through the East Greenland Current. These anomalies then propagate around the subpolar gyre into the Labrador Sea and the central North Atlantic. These oscillations are coherent with previously identified multi-decadal fluctuations in the intensity of the North Atlantic thermohaline circula- tion. The oscillations in the G:eenland Sea are related to atmospheric variability. Negative (cold) anomalies of surface air temperature are associated with negative (cold) sea surface temperature (SST) anomalies in the Greenland Sea, with amplitudes up to 2oC near Green- land declining to several tenths of a degree C over north- western Europe. The c01d SST anomalies and intensified East Greenland Current are also associated with enhanced northerly winds over the Greenland Sea.

The Impact of Ocean Initial Conditions on ENSO Forecasting with a Coupled Model

Abstract: A coupled atmosphere–ocean GCM (general circulation model) has been developed for climate predictions on seasonal to interannual timescales. The atmosphere model is a global spectral GCM T30L18 and the ocean model is global on a 1° grid. Initial conditions for the atmosphere were obtained from National Meteorological Center (now known as the National Centers for Environmental Prediction) analyses, while those for the ocean came from three ocean data assimilation (DA) systems. One system is a four-dimensional DA scheme that uses conventional SST observations and vertical temperature profiles inserted into the ocean model and is forced from winds from an operational analysis. The other two initialization schemes are based on the coupled model, both nudging the surface temperature toward observed SSTs and one nudging surface winds from an operational analysis. All three systems were run from 1979 to 1988, saving the state of the ocean every month, thus initial conditions may be obtained for any mont...

Radiative forcing of climate from halocarbon-induced global stratospheric ozone loss

Abstract: OBSERVATIONS from satellite and ground-based instruments1–3 indicate that between 1979 and 1990 there have been statistically significant losses of ozone in the lower stratosphere of the middle to high latitudes in both hemispheres. Here we determine the radiative forcing of the surface–troposphere system4–6 due to the observed decadal ozone losses, and compare it with that due to the increased concentrations of the other main radiatively active gases (CO2, CH4, N2O and chlorofluorocarbons) over the same time period. Our results indicate that a significant negative radiative forcing results from ozone losses in middle to high latitudes, in contrast to the positive forcing at all latitudes caused by the CFCs and other gases. As the anthropogenic emissions of CFCs and other halocarbons are thought to be largely responsible for the observed ozone depletions1, our results suggest that the net decadal contribution of CFCs to the greenhouse climate forcing is substantially less than previously estimated.

Past, Present, and Future Changes in the Atlantic Meridional Overturning Circulation

Abstract: Observations and numerical modeling experiments provide evidence for links between variability in the Atlantic meridional overturning circulation (AMOC) and global climate patterns. Reduction in the strength of the overturning circulation is thought to have played a key role in rapid climate change in the past and may have the potential to significantly influence climate change in the future, as noted in the last two Intergovernmental Panel on Climate Change (IPCC) assessment reports (Houghton et al.; Solomon et al.). Both IPCC reports also highlighted the significant uncertainties that exist regarding the future behavior of the AMOC under global warming. Model results suggest that changes in the AMOC can impact surface air temperature, precipitation patterns, and sea level, particularly in areas bordering the North Atlantic, thus affecting human populations. Here, the current understanding of past, present, and future changes in the AMOC and the effects of such changes on climate are reviewed. The focus is on observations of the AMOC, how the AMOC influences climate, and in what way the AMOC is likely to change over the next few decades and the twenty-first century. The potential for decadal prediction of the AMOC is also discussed. Finally, the outstanding challenges and possible future directions for AMOC research are outlined.

Data‐based estimates of suboxia, denitrification, and N2O production in the ocean and their sensitivities to dissolved O2

Abstract: [1] Oxygen minimum zones (OMZs) are major sites of fixed nitrogen removal from the open ocean However, commonly used gridded data sets such as the World Ocean Atlas (WOA) tend to overestimate the concentration of O2 compared to measurements in grids where O2 falls in the suboxic range (O2 < 2–10 mmol m−3), thereby underestimating the extent of O2 depletion in OMZs We evaluate the distribution of the OMZs by (1) mapping high-quality oxygen measurements from the WOCE program, and (2) by applying an empirical correction to the gridded WOA based on in situ observations The resulting suboxic volumes are a factor 3 larger than in the uncorrected gridded WOA We combine the new oxygen data sets with estimates of global export and simple models of remineralization to estimate global denitrification and N2O production We obtain a removal of fixed nitrogen of 70 ± 50 Tg year−1 in the open ocean and 198 ± 64 Tg year−1 in the sediments, and a global N2O production of 62 ± 32 Tg year−1 Our results (1) reconcile water column denitrification rates based on global oxygen distributions with previous estimates based on nitrogen isotopes, (2) revise existing estimates of sediment denitrification down by 1/3d through the use of spatially explicit fluxes, and (3) provide independent evidence supporting the idea of a historically balanced oceanic nitrogen cycle These estimates are most sensitive to uncertainties in the global export production, the oxygen threshold for suboxic processes, and the efficiency of particle respiration under suboxic conditions Ocean deoxygenation, an expected response to anthropogenic climate change, could increase denitrification by 14 Tg year−1 of nitrogen per 1 mmol m−3 of oxygen reduction if uniformly distributed, while leaving N2O production relatively unchanged