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GFDL Research Highlights

April 6th, 2012 - An Overview of CMIP5 and the Experiment Design

The fifth phase of the Coupled Model Intercomparison Project (CMIP5) will produce a coordinated multi-model dataset that is designed to advance our knowledge of climate variability and climate change. Researchers worldwide will analyze the model output and produce results that will underlie the forthcoming IPCC Fifth Assessment Report. Unprecedented in scale, CMIP5 has attracted participation from all major climate modeling groups. Building on previous CMIP efforts, CMIP5 includes “long-term” simulations of 20th century climate and projections for the 21st century and beyond . Read More…

March 29th, 2012 - Reducing Uncertainty in Understanding Ocean Oxygen and Nitrogen Cycles

Oxygen minimum zones (OMZs) exclude many classes of the biological community and are major sites of fixed nitrogen removal from the open ocean. Previous estimates of rates of fixed nitrogen loss through denitrification in the pelagic ocean and in sediments have been unable to match estimates of the supply of fixed nitrogen via N2 fixation, rivers, and atmospheric deposition. This has led some scientists to the conclusion that the global ocean nitrogen cycle is out of balance, and the oceans are accumulating fixed nitrogen. 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 1 where O2 falls in the suboxic range (O2 < 2 – 10 μM), thereby underestimating the extent of O2 depletion in OMZs. Read More…

March 12th, 2012 - A Model Study of Heat Waves over North America: Meteorological Aspects and Projections for the 21st Century

The goal of this research is to evaluate the fidelity of GFDL climate models in reproducing the characteristics of summertime heat waves in North America, and to examine the model-projected changes of these characteristics in the 21st century.

North American incurs considerable economic costs due to heat waves. Understanding of the processes contributing to heat waves, and projecting changes in their characteristics in the 21st century, are an integral part of the NOAA mission to provide scientific information on the present and future states of the climate system. Read More…

February 24th, 2012 - Transport of Asian ozone pollution into surface air over the western United States in spring

As Asian countries develop, they are emitting more ozone precursors that pollute surface level air. Many studies have documented this pollution being carried by air currents to the western United States. To determine the extent to which this pollution is affecting air quality in the western U.S., we analyzed balloon soundings, aircraft, surface and satellite measurements from May through June 2010 using a new global high-resolution chemistry-climate model. Our findings indicate that Asian pollution contributes as much as 20 percent of total ozone during springtime pollution episodes in western U.S. surface air. Read More…

February 14th, 2012 - Will open ocean oxygen stress intensify under climate change?

Ten percent of today’s ocean volume is characterized by low level of dissolved oxygen similar to those found in the well-known “dead zones” in the Gulf of Mexico with 35% of global surface waters overlying at least some of this “hypoxia” (O2 < 88 µM;2ml l-1). Under global warming, higher temperatures would be expected to directly lower oxygen concentrations and enhanced stratification to reduce the flow of well-ventilated surface waters to the interior. Under such circumstances, it has been hypothesized that the open-ocean dead zones could greatly expand and indeed changes in low-oxygen waters have been invoked as evidence of climate change. Read More…

January 24th, 2012 - Pathways Between Primary Production and Fisheries Yields of Large Marine Ecosystems

There is considerable uncertainty in projections of the impacts of climate on fisheries yields due to uncertainties in climate change impacts on primary production and the processes controlling how much primary production is transferred to fish. Primary production and proxies such as chlorophyll have proven to be useful predictors of fisheries yields at regional scales but show much less skill when applied globally. The marine food web dynamics that control the transfer of energy from phytoplankton to fish are complex and the relationship between primary production and fisheries production may differ dramatically between ecosystems due to changes in planktonic food web structure. Read More…

September 29th, 2011 - Anthropogenic Aerosols and the Weakening of the South Asian Summer Monsoon

An important part of the global water cycle, the South Asian summer monsoon provides about 80% of the region’s annual precipitation, and touches the lives of more than 20% of the world’s population. Using the NOAA/GFDL state-of-the-art global climate model that accounts for all the known natural and anthropogenic forcings, we have investigated what caused the observed decrease in the South Asian summer monsoon rainfall over the second half of the 20th century. Was the widespread drying due to natural factors or human activities? If the latter, what were the relative contributions of anthropogenic greenhouse gases and aerosols? Answering these questions poses a challenging test on our fundamental knowledge of the changes to the Earth’s hydrological cycle, and on our ability to understand and project future regional climate change. Read More…

September 12th, 2011 - Climatological characteristics of Arctic and Antarctic surface-based inversions

Surface-based inversions (SBI) are frequent features of the Arctic and Antarctic atmospheric boundary layer and influence important climate processes. However, prior to this study, climatological polar SBI properties had not been fully characterized, nor had climate model simulations of SBIs been compared comprehensively to observations. Using 20 years of radiosonde observations, and simulations from two state-of-the-art climate models, this study examines the spatial and temporal variability of three SBI characteristics – frequency of occurrence, depth (from the surface to the inversion top), and intensity (temperature difference over the SBI depth) – and relationships among them. Read More…

July 3rd, 2011 - Different magnitudes of projected subsurface ocean warming around Greenland and Antarctica

Recent acceleration of Greenland and Antarctic outlet glaciers and ice flows is closely linked to ocean warming, especially in the subsurface layer. This land ice melt will cause sea level rise.

We find that in response to an increase in atmospheric greenhouse-gas concentrations, the subsurface oceans (200-500 m) surrounding the two polar ice sheets both warm substantially more than has been observed thus far. Model projections suggest that the maximum ocean warming around Greenland will be double the global mean, whereas ocean warming around Antarctica will be only half the global mean. Read More…

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