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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Contribution of Phycoerythrin-Containing Phytoplankton to Remotely Sensed Signals in the Ocean

The purpose of this project was to evaluate the importance of phycoerythrin-containing phytoplankton, in particular coccoid cyanobacteria, to remote sensing. We proposed to estimate cyanobacteria abundance and pigmentation and their relationship to water-column optics. We have estimated the contribution of cyanobacteria to scattering and backscattering in both open ocean (Sargasso Sea) and coastal waters (western coast of North Atlantic and the California Current). Sampling and data processing is performed. Relationship between water column optics and phycoerythrin concentration and algorithms development are being carried out.

Vernet, Maria↗
NASA NTRS2012

A "Warm Formamide" Scenario for the Origins of Life Might not be so Hot: Comment on "Formamide and the Origin of Life"

In this review, Saladino et al. present an intriguing hypothesis surrounding the role of formamide in the origins of life on Earth, backed by experimental results supporting each step from formamide to RNA polymers. The overall premise is that, from formamide and inorganic phosphate, RNA molecules over 100 nucleotides in length can be produced. In addition, many carboxylic acids likely relevant to prebiotic metabolism, are formed along the way. Thus, from a rather simple organic molecule that has been observed in outer space (formamide), you can generate many of the compounds necessary for the origins of life. However, because high temperatures (160 C) are required for the formamide reactions, it remains unclear where the "warm formamide" scenario could have occurred. Low-temperature, aqueous hydrogen cyanide-based prebiotic chemistry that we know actually happened has been shown to produce many of the molecules invoked in the formamide hypothesis: amino acids, carboxylic acids, sugar acids, and nucleobases have all been found in meteorites recovered on Earth, providing a plausible route for their synthesis and delivery. In contrast, a large portion of the formamide hypothesis is based on relatively hightemperature reactions, A plausible milieu for high-temperature reactions with concentrated formamide is yet to be described, and is critical for this hypothesis to be validated. Hydrothermal vents are attractive heat sources, and the higher boiling point of formamide has been invoked as a mechanism to concentrate it from an aqueous solution, Unless the water can actually evaporate, however, there would be no net enrichment. For example, in the context of a deep-sea vent, any water "removed" by heating would be quickly replaced. Some of the individual reactions underpinning the present hypothesis have been met with skepticism because they go against conventional wisdom, To name a few of the surprising results: the observation that nucleosides can be converted to cyclic phosphates when heated in the presence of minerals and inorganie phosphate; that 3'-5' cGMP and cAMP nucleotides polymerize rapidly into RNA oligomers, even in the absence of monovalent counterions and that end-to-end ligation reactions between RNA oligomers occur in essentially pure water, without requiring any activating groups or counterions. Because the polymerization reactions are simply transesterification reactions, that they readily occur in the absence of cations makes one wonder why nearly all ribozyme-catalyzed transesterification reactions are metal-ion dependent; similarly, that the end-to-end ligation reactions do not require activation runs counter to the observation that all protein-catalyzed ligation and polymerization reactions of RNA and DNA require activated substrates. Detailed mechanistic studies of the reported reactions are warranted and could provide important insights for understanding the chemistry behind the origins of life. Because the authors have produced many of the experimental results supporting their hypothesis, they could demonstrate the validity of their hypothesis by converting formamide into approx 100 nucleotide RNA oligomers, using the products of one reaction as the reactants for the next reaction, under specific conditions plausible on the pre-biotic Earth. Such a demonstration would represent a milestone for our understanding of the origins of life.

Burton, Aaron S.↗
NASA NTRS2012

Arctic PBL Cloud Height and Motion Retrievals from MISR and MINX

How Arctic clouds respond and feedback to sea ice loss is key to understanding of the rapid climate change seen in the polar region. As more open water becomes available in the Arctic Ocean, cold air outbreaks (aka. off-ice flow from polar lows) produce a vast sheet of roll clouds in the planetary boundary layer (PBl). The cold air temperature and wind velocity are the critical parameters to determine and understand the PBl structure formed under these roll clouds. It has been challenging for nadir visible/IR sensors to detect Arctic clouds due to lack of contrast between clouds and snowy/icy surfaces. In addition) PBl temperature inversion creates a further problem for IR sensors to relate cloud top temperature to cloud top height. Here we explore a new method with the Multiangle Imaging Spectro-Radiometer (MISR) instrument to measure cloud height and motion over the Arctic Ocean. Employing a stereoscopic-technique, MISR is able to measure cloud top height accurately and distinguish between clouds and snowy/icy surfaces with the measured height. We will use the MISR INteractive eXplorer (MINX) to quantify roll cloud dynamics during cold-air outbreak events and characterize PBl structures over water and over sea ice.

Wu, Dong L.↗
NASA NTRS2012

A 'Warm Formamide' Scenario for the Origins of Life Might Not Be so Hot Comment on 'Formamide and the Origin of Life' by E. Di Mauro Et Al.

In this review, Saladino et al. present an intriguing hypothesis surrounding the role of formamide in the originsof life on Earth, backed by experimental results supporting each step from formamide to RNA polymers [1]. The overall premise is that, from formamide and inorganic phosphate, RNA molecules over 100 nucleotides in length canbe produced. In addition, many carboxylic acids likely relevant to prebiotic metabolism are formed along the way. Thus, from a rather simple organic molecule that has been observed in outer space (formamide), you can generatemany of the compounds necessary for the origins of life. However, because high temperatures (160 C) are requiredfor the formamide reactions, it remains unclear where the warm formamide scenario could have occurred.Low-temperature, aqueous hydrogen counter to the observation that all protein-catalyzed ligation and polymerization reactions of RNA and DNA requireactivated substrates. Detailed mechanistic studies of the reported reactions are warranted and could provide important insights for understanding the chemistry behind the origins of life.Because the authors have produced many of the experimental results supporting their hypothesis, they coulddemonstrate the validity of their hypothesis by converting formamide into 100 nucleotide RNA oligomers, usingthe products of one reaction as the reactants for the next reaction, under specific conditions plausible on the pre-bioticEarth. Such a demonstration would represent a milestone for our understanding of the origins of life.cyanide-based prebiotic chemistry that we know actually happened has beenshown to produce many of the molecules invoked in the formamide hypothesis: amino acids, carboxylic acids, sugaracids, and nucleobases have all been found in meteorites recovered on Earth [e.g. [24]], providing a plausible routefor their synthesis and delivery. In contrast, a large portion of the formamide hypothesis is based on relatively high-temperature reactions. A plausible milieu for high-temperature reactions with concentrated formamide is yet to bedescribed, and is critical for this hypothesis to be validated. Hydrothermal vents are attractive heat sources, and the higher boiling point of formamide has been invoked as a mechanism to concentrate it from an aqueous solution.Unless the water can actually evaporate, however, there would be no net enrichment. For example, in the context of a deep-sea vent, any water removed by heating would be quickly replaced.Some of the individual reactions underpinning the present hypothesis [1] have been met with skepticism becausethey go against conventional wisdom. To name a few of the surprising results: the observation that nucleosides can beconverted to cyclic phosphates when heated in the presence of minerals and inorganic phosphate [5]; that 35 cGMPand cAMP nucleotides polymerize rapidly into RNA oligomers, even in the absence of monovalent counterions [6];and that end-to-end ligation reactions between RNA oligomers occur in essentially pure water, without requiring any activating groups or counterions [7,8]. Because the polymerization reactions are simply transesterification reactions,that they readily occur in the absence of cations makes one wonder why nearly all ribozyme-catalyzed transesterification reactions are metal-ion dependent; similarly, that the end-to-end ligation reactions do not require activation runs.

life↗
DOE OSTI2026

Assessing shellfish water exposure to fecal bacteria pollution in Salish Sea: three-dimensional modeling and implications for monitoring

Fecal bacteria (FB) contamination poses significant risks to shellfish safety and management in coastal and estuarine waters. Despite extensive pollution identification and correction efforts, FB contamination in shellfish-growing areas persists in the Salish Sea, highlighting the need to identify overlooked sources and better understand FB transport from riverine and shoreline inputs to shellfish beds. To address this, a high-resolution three-dimensional hydrodynamic model coupled with FB kinetics was developed and applied to a case study site in Salish Sea—Portage Bay—to simulate freshwater plume circulation, flushing dynamics, and bacterial transport. Daily FB loading from the major freshwater inflow—Nooksack River was generated by both linear interpolation and integrating a machine learning approach (XGBoost), trained on historical hydrological and meteorological data. The model successfully reproduced both the magnitude and seasonal variation of FB concentrations in Portage Bay for the year of 2021, demonstrating that simplified FB kinetics with first-order decay due to mortality was effective in this dynamic coastal environment with short flushing time. Model results identified the Nooksack River as the dominant far-field FB source, while scenario simulations showed that near-field coastal stormwater outfalls elevated local FB levels following rainfall, particularly under low-flow conditions. The XGBoost prediction provided comparable or superior accuracy to linear interpolation, particularly during periods of missing observational data, by capturing short-term variability and event-driven loading more effectively. Integrating data-driven riverine FB inputs with mechanistic coastal numerical modeling provides a robust framework for operational forecasting of shellfish bed exposure risk and supports adaptive monitoring and management of shellfish growing areas in the Salish Sea and similar coastal systems.

Salish Sea↗
DOE OSTI2020

Multi-Element Water Content System Instrument Handbook

The SEA Model WCM-2000 multi-element water content system was designed to provide aircraft and wind tunnel users with a single, rugged sensor to simultaneously measure liquid water content (LWC), total water content (TWC), and ice water content (IWC). The instrument consists of four heated stainless steel elements, each with a different shape or size. Each element is directly heated by low-voltage DC current flowing through the element. These elements are maintained at a constant temperature, typically 140°C, by a digital closed-loop control system. Three of the heated elements are exposed directly to the airstream and incoming cloud water. A fourth element, the reference/comp element, is arranged to be exposed to the airflow but not to incoming cloud water. This element is used to establish the “dry power term” that is subtracted from the other three elements’ power readings to establish the measured water content.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2004

ICESat Observations of Arctic Sea Ice: A First Look

Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice free-board along the altimeter tracks. This step is necessitated by the large uncertainties in the time-varying sea surface topography compared to that required for accurate determination of free-board. Unknown snow depth introduces the largest uncertainty in the conversion of free-board to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint.

Kwok, Ron↗
NASA NTRS2004

ICESat Observations of Arctic Sea Ice: A First Look

Analysis of near-coincident ICESat and RADARSAT imagery shows that the retrieved elevations from the laser altimeter are sensitive to new openings (containing thin ice or open water) in the sea ice cover as well as to surface relief of old and first-year ice. The precision of the elevation estimates, measured over relatively flat sea ice, is approx. 2 cm. Using the thickness of thin-ice in recent openings to estimate sea level references, we obtain the sea-ice freeboard along the altimeter tracks. This step is necessitated by the large uncertainties in the sea surface topography compared to that required for accurate determination of freeboard. Unknown snow depth introduces the largest uncertainty in the conversion of freeboard to ice thickness. Surface roughness is also derived, for the first time, from the variability of successive elevation estimates along the altimeter track. Overall, these ICESat measurements provide an unprecedented view of the Arctic Ocean ice cover at length scales at and above the spatial dimension of the altimeter footprint of approx. 70 m.

Arctic Ocean↗
NASA NTRS2011

Introduction to: Atlantic Meridional Overturning Circulation(AMOC)

A striking conclusion of the Intergovernmental Panel on Climate Change 2007 report is the crucial role that the Atlantic Meridional Overturning Circulation (AMOC) may play in anthropogenic climate change. However, these IPCC coupled climate simulations show a broad range of uncertainty in the magnitude and timing of AMOC transport change ranging from none to nearly complete collapse within the 21st century. The potential consequences of large changes in the characteristics of AMOC have motivated the creation in the United States of an interagency program and implementation plan to develop monitoring and prediction capabilities for the AMOC This program parallels the development of substantial monitoring efforts by European, South American and African countries -- notably the UK Rapid and Rapid-Watch programs. The papers contained in this volume are derived from presentations at the First U.S. Atlantic Meridional Overturning Circulation (AMOC) Meeting held 4 - 6 May, 2009 to review the US implementation plan and its coordination with other monitoring activities. The Atlantic Meridional Overturning Circulation consists of multiple components illustrated in an attached figure. Water enters the South Atlantic at upper and intermediate depths through both western and eastern routes (where eddy transport is especially important) and is transported northward across the equator, where it recirculates within the northern subtropical and subpolar gyres. The northern end is defined by the sinking regions of the Nordic Seas and the Labrador Sea where the waters that eventually form the upper and lower branches of North Atlantic Deep Water are conditioned. High surface salinities, the result of high net evaporation in the tropics and subtropics (including the Mediterranean Sea), and presence of regions of the Arctic Ocean that remain ice-free even in winter allow for the rapid cooling and thus densification of surface water. This dense surface water becomes the source of deep water formation in the sinking regions. In addition to transporting mass, the AMOC transports roughly half of the total amount of heat carried northward through the northern subtropics (down the temperature-gradient) by the ocean. In contrast in the Southern Hemisphere AMOC transports heat up-gradient from the cool Circumpolar Current to the warm tropics. Paleoevidence suggests that AMOC heat transport in the two hemispheres has varied over time in ways intimately tied to millennial changes in the Earth's climate. In one example, the abrupt Younger Dryas spell of cold weather over the North Atlantic, which began 13,000 years ago, has generally been linked to a millennial shutdown of the AMOC as a result of massive freshwater discharge from the North American continent. The current AMOC monitoring array consists of a series of instrumented transects located across key passages (see Cunningham et al., 2010 for a recent review). In the Arctic and sub-Arctic, transects cross Fram Strait, Denmark Strait and the Faroe Channel (connecting Greenland, Iceland, and the United Kingdom), as well as the entrance to the Labrador Sea. Further south and extending outwards from the east coast of North America there are a series of monitoring arrays including arrays of the Canadian Atlantic Zone Monitoring Program, deployments of the Rapid Western Atlantic Variability Experiment (WAVE), Line W at 39 N, as well as the Rapid-MOC moored array. The latter spans the entire Atlantic basin along 26.5 N. At tropical latitudes we have the Meridional Overturning Variability Experiment (MOVE) array at 16 N, while in the Southern Hemisphere a corresponding basin-spanning transect is being established at the latitude of Cape of Good Hope, complemented by arrays at Drake Passage.

Hakkinen, Sirpa↗
NASA NTRS1999

Seasonal-to-Interannual Variability in Antarctic Sea-Ice Dynamics, and Its Impact on Surface Fluxes and Water Mass Production

Strong seasonal and interannual signals in Antarctic bottom-water outflow remain unexplained yet are highly correlated with anomalies in net sea-ice growth in coastal polynyas. The mechanisms responsible for driving salination and replenishment and rejuvenation of the dense shelf "source" waters likely also generate pulses of bottom water outflow. The objective of this research is to investigate time-scales of variability in the dynamics of sea-ice in the Southern Ocean in order to determine the primary sites for production of dense shelf waters. We are using a merged satellite/buoy sea-ice motion data set for the period 1978-present day to compute the dynamics of opening and closing of coastal polynyas over the continental shelf. The Ocean Circulation and Climate Advanced Model (OCCAM) ocean general circulation model with coupled sea-ice dynamics is presently forced using National Center for Environmental Prediction (NCEP) data to simulate fluxes and the salination impact of the ocean shelf regions. This work is relevant in the context of measuring the influence of polar sea-ice dynamics upon polar ocean characteristics, and thereby upon global thermohaline ocean circulation. Interannual variability in simulated net freezing rate in the Southern Weddell Sea is shown for the period 1986-1993. There is a pronounced maximum of ice production in 1988 and minimum in 1991 in response to anomalies in equatorward meridional wind velocity. This follows a similar approximate 8-year interannual cycle in Sea Surface Temperature (SST) and satellite-derived ice-edge anomalies reported elsewhere as the "Antarctic Circumpolar Wave." The amplitude of interannual fluctuations in annual net ice production are about 40% of the mean value, implying significant interannual variance in brine rejection and upper ocean heat loss. Southward anomalies in wind stress induce negative anomalies in open water production, which are observed in passive microwave satellite images. Thus, cycles of enhanced poleward wind stress reduce ice growth by compacting the ice along the coastline and closing open water in leads and polynyas. Model simulations confirm that years of low ice production, such as 1991, coincide with years of lower than normal bottom water outflow. Future plans include the assimilation of satellite ice concentrations and ice drift dynamics to more accurately constrain boundary conditions in the model.

Drinkwater, Mark R.↗
NASA NTRSDate not supplied

Exploring the Elevated Water Vapor Signal Associated With the Free Tropospheric Biomass Burning Plume Over the Southeast Atlantic Ocean

In southern Africa, widespread agricultural fires produce substantial biomass burning (BB) emissions over the region. The seasonal smoke plumes associated with these emissions are then advected westward over the persistent stratocumulus cloud deck in the southeast Atlantic (SEA) Ocean, resulting in aerosol effects which vary with time and location. Much work has focused on the effects of these aerosol plumes, but previous studies have also described an elevated free tropospheric water vapor signal over the SEA. Water vapor influences climate in its own right, and it is especially important to consider atmospheric water vapor when quantifying aerosol–cloud interactions and aerosol radiative effects. Here we present airborne observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign over the SEA Ocean. In observations collected from multiple independent instruments on the NASA P-3 aircraft (from near-surface to 6–7 km), we observe a strongly linear correlation between pollution indicators (carbon monoxide (CO) and aerosol loading) and atmospheric water vapor content, seen at all altitudes above the boundary layer. The focus of the current study is on the especially strong correlation observed during the ORACLES-2016 deployment (out of Walvis Bay, Namibia), but a similar relationship is also observed in the August 2017 and October 2018 ORACLES deployments. Using reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and specialized WRF-Chem simulations, we trace the plume–vapor relationship to an initial humid, smoky continental source region, where it mixes with clean, dry upper tropospheric air and then is subjected to conditions of strong westward advection, namely the southern African easterly jet (AEJ-S). Our analysis indicates that air masses likely left the continent with the same relationship between water vapor and carbon monoxide as was observed by aircraft. This linear relationship developed over the continent due to daytime convection within a deep continental boundary layer (up to ∼5–6 km) and mixing with higher-altitude air, which resulted in fairly consistent vertical gradients in CO and water vapor, decreasing with altitude and varying in time, but this water vapor does not originate as a product of the BB combustion itself. Due to a combination of conditions and mixing between the smoky, moist continental boundary layer and the dry and fairly clean upper-troposphere air above (∼6 km), the smoky, humid air is transported by strong zonal winds and then advected over the SEA (to the ORACLES flight region) following largely isentropic trajectories. Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) back trajectories support this interpretation. This work thus gives insights into the conditions and processes which cause water vapor to covary with plume strength. Better understanding of this relationship, including how it varies spatially and temporally, is important to accurately quantify direct, semi-direct, and indirect aerosol effects over this region.

Kristina Pistone↗
DOE OSTI2021

Exploring the elevated water vapor signal associated with the free tropospheric biomass burning plume over the southeast Atlantic Ocean

In southern Africa, widespread agricultural fires produce substantial biomass burning (BB) emissions over the region. The seasonal smoke plumes associated with these emissions are then advected westward over the persistent stratocumulus cloud deck in the southeast Atlantic (SEA) Ocean, resulting in aerosol effects which vary with time and location. Much work has focused on the effects of these aerosol plumes, but previous studies have also described an elevated free tropospheric water vapor signal over the SEA. Water vapor influences climate in its own right, and it is especially important to consider atmospheric water vapor when quantifying aerosol-cloud interactions and aerosol radiative effects. Here we present airborne observations made during the NASA ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) campaign over the SEA Ocean. In observations collected from multiple independent instruments on the NASA P-3 aircraft (from near-surface to 6-7 km), we observe a strongly linear correlation between pollution indicators (carbon monoxide (CO) and aerosol loading) and atmospheric water vapor content, seen at all altitudes above the boundary layer. The focus of the current study is on the especially strong correlation observed during the ORACLES-2016 deployment (out of Walvis Bay, Namibia), but a similar relationship is also observed in the August 2017 and October 2018 ORACLES deployments. Using reanalyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), and specialized WRF-Chem simulations, we trace the plume-vapor relationship to an initial humid, smoky continental source region, where it mixes with clean, dry upper tropospheric air and then is subjected to conditions of strong westward advection, namely the southern African easterly jet (AEJ-S). Our analysis indicates that air masses likely left the continent with the same relationship between water vapor and carbon monoxide as was observed by aircraft. This linear relationship developed over the continent due to daytime convection within a deep continental boundary layer (up to ~5-6 km) and mixing with higher-altitude air, which resulted in fairly consistent vertical gradients in CO and water vapor, decreasing with altitude and varying in time, but this water vapor does not originate as a product of the BB combustion itself. Due to a combination of conditions and mixing between the smoky, moist continental boundary layer and the dry and fairly clean upper-troposphere air above (~6 km), the smoky, humid air is transported by strong zonal winds and then advected over the SEA (to the ORACLES flight region) following largely isentropic trajectories. Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) back trajectories support this interpretation. This work thus gives insights into the conditions and processes which cause water vapor to covary with plume strength. Better understanding of this relationship, including how it varies spatially and temporally, is important to accurately quantify direct, semi-direct, and indirect aerosol effects over this region.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2024

Steric Sea Level Rise and Relationships with Model Drift and Water Mass Representation in GFDL CM4 and ESM4

Abstract Density-driven steric seawater changes are a leading-order contributor to global mean sea level rise. However, intermodel differences in the magnitude and spatial patterns of steric sea level rise exist at regional scales and often emerge during the spinup and preindustrial control integrations of climate models. Steric sea level results from an eddy-permitting climate model, GFDL CM4, are compared with a lower-resolution counterpart, GFDL-ESM4. The results from both models are examined through basin-scale heat budgets and watermass analysis, and we compare the patterns of ocean heat uptake, redistribution, and sea level differ in ocean-only [i.e., Ocean Model Intercomparison Project (OMIP)] and coupled climate configurations. After correcting for model drift, both GFDL CM4 and GFDL-ESM4 simulate nearly equivalent ocean heat content change and global sea level rise during the historical period. However, the GFDL CM4 model exhibits as much as a 40% increase in surface ocean heat uptake in the Southern Ocean and subsequent increases in horizontal export to other ocean basins after bias correction. The results suggest regional differences in the processes governing Southern Ocean heat export, such as the formation of Antarctic Intermediate Water (AAIW), Subpolar Mode Water (SPMW), and gyre transport between the two models, and that sea level changes in these models cannot be fully bias-corrected. Since the process-level differences between the two models are evident in the preindustrial control simulations of both models, these results suggest that the control simulations are important for identifying and correcting sea level–related model biases.

Krasting, John P. [a NOAA/OAR/Geophysical Fluid Dy↗
NASA NTRS2013

Teleconnections, Midlatitude Cyclones and Aegean Sea Turbulent Heat Flux Variability on Daily Through Decadal Time Scales

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 deep water 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 (NCP), 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.

cyclones↗
NASA NTRS2005

Global monitoring of Sea Surface Salinity with Aquarius

Aquarius is a microwave remote sensing system designed to obtain global maps of the surface salinity field of the oceans from space. It will be flown on the Aquarius/SAC-D mission, a partnership between the USA (NASA) and Argentina (CONAE) with launch scheduled for late in 2008. The objective of Aquarius is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This will provide data to address scientific questions associated with ocean circulation and its impact on climate. For example, salinity is needed to understand the large scale thermohaline circulation, driven by buoyancy, which moves large masses of water and heat around the globe. Of the two variables that determine buoyancy (salinity and temperature), temperature is already being monitored. Salinity is the missing variable needed to understand this circulation. Salinity also has an important role in energy exchange between the ocean and atmosphere, for example in the development of fresh water lenses (buoyant water that forms stable layers and insulates water below from the atmosphere) which alter the air-sea coupling. Aquarius is a combination radiometer and scatterometer (radar) operating at L-band (1.413 GHz for the radiometer and 1.26 GHz for the scatterometer). The primary instrument,for measuring salinity is the radiometer which is able to detect salinity because of the modulation salinity produces on the thermal emission from sea water. This change is detectable at the long wavelength end of the microwave spectrum. The scatterometer will provide a correction for surface roughness (waves) which is one of the greatest unknowns in the retrieval. The sensor will be in a sun-synchronous orbit at about 650 km with equatorial crossings of 6am/6pm. The antenna for these two instruments is a 3 meter offset fed reflector with three feeds arranged in pushbroom fashion looking away from the sun toward the shadow side of the orbit to minimize sunglint. The mission goal is to produce maps of the salinity field globally once each month with an accuracy of 0.2 psu and a spatial resolution of 100 km. This will be adequate to address l&ge scale features of the salinity field of the open ocean. The temporal resolution is sufficient to address seasonal changes and a three year mission is planned to-collect sufficient data to look for interannual variation. Aquarius is being developed by NASA as part of the Earth System Science Pathfinder (ESSP) program. The SAC-D mission is being developed by CONAE and will include the space craft and several additional instruments, including visible and infrared cameras and a microwave radiometer to monitor rain and wind velocity over the oceans, and sea ice.

Lagerloef, G. S. E.↗
NASA NTRS1976

Ocean color spectra measured off the Oregon coast - Characteristic vectors

The ocean color spectrum is defined as the ratio of the spectrum of light upwelled from the sea to the spectrum of light incident on the sea surface. Ocean color spectra, observed from an airplane flown over waters off Oregon, are analyzed. The original spectra are resolved into fifty-five wavelength bands, each 5 nm wide. The shapes of these spectra are parameterized by, and shown to be accurately recoverable from, their first four principal components. These components are the scalar projections of each spectrum on the first four characteristic vectors of the sample covariance matrix. Regression equations are found with which phytoplankton pigment concentration and water transparency may be estimated as linear functions of the principal components. Pigment concentration estimates thus obtained are imprecise. The poor fit is at least partly due to the inappropriateness of the linear regression model and the neglect of other optically important substances typically present in sea water.

Mueller, J. L.↗
NASA NTRS1998

Variability of Arctic Sea Ice as Viewed from Space

Over the past 20 years, satellite passive-microwave radiometry has provided a marvelous means for obtaining information about the variability of the Arctic sea ice cover and particularly about sea ice concentrations (% areal coverages) and from them ice extents and the lengths of the sea ice season. This ability derives from the sharp contrast between the microwave emissions of sea ice versus liquid water and allows routine monitoring of the vast Arctic sea ice cover, which typically varies in extent from a minimum of about 8,000,000 sq km in September to a maximum of about 15,000,000 sq km in March, the latter value being over 1.5 times the area of either the United States or Canada. The vast Arctic ice cover has many impacts, including hindering heat, mass, and y momentum exchanges between the oceans and the atmosphere, reducing the amount of solar radiation absorbed at the Earth's surface, affecting freshwater transports and ocean circulation, and serving as a vital surface for many species of polar animals. These direct impacts also lead to indirect impacts, including effects on local and perhaps global atmospheric temperatures, effects that are being examined in general circulation modeling studies, where preliminary results indicate that changes on the order of a few percent sea ice concentration can lead to temperature changes of 1 K or greater even in local areas outside of the sea ice region. Satellite passive-microwave data for November 1978 through December 1996 reveal marked regional and interannual variabilities in both the ice extents and the lengths of the sea ice season, as well as some statistically significant trends. For the north polar ice cover as a whole, maximum ice extents varied over a range of 14,700,000 - 15,900,000 km(2), while individual regions showed much greater percentage variations, e.g., with the Greenland Sea experiencing a range of 740,000 - 1,1110,000 km(2) in its yearly maximum ice coverage. Although variations from year to year and region to region are large, overall the Arctic ice extents did show a statistically significant, 2.8%/ decade negative trend over the 18.2-year period. Ice season lengths, which vary from only a few weeks near the ice margins to the full year in the large region of perennial ice coverage, also experienced interannual variability, and mapping their trends allows detailed geographic information on exactly where the ice season lengthened and where it shortened. Over the 18 years, ice season lengthening occurred predominantly in the western hemisphere and was strongest in the western Labrador Sea, while ice season shortening occurred predominantly in the eastern hemisphere and was strongest in the eastern Barents Sea. Much information about other important Arctic sea ice variables has also been obtained from satellite data, including information about melt ponding, temperature, snow cover, and ice velocities. For instance, maps of ice velocities have now been made from satellite scatterometry data, including information about melt ponding, temperature, snow cover, and ice velocities.

Parkinson, Claire L.↗
NASA NTRS1975

A generalized tensor formulation of atmosphere and seas dynamics

A generalized mathematical model was developed for simulation of the dynamics and transport of both the atmosphere and seas. A nearly horizontal bottom coordinate surface conforms to the land-to-air interface and the sea-floor-to-water interface, which simplifies computations. General vertical motion of the other quasi-horizontal coordinate surfaces is allowed; external gravity waves can be represented by the top coordinate surface, and meteorological fronts and inversion layers in the atmosphere and refractive layers in the seas can be represented with enhanced resolution by the internal quasi-horizontal coordinate surfaces. A tensor reformulation of the standard subgrid mixing theory departs significantly from the standard theory in allowing, as a solution under adiabatic conditions, rigid-body rotation of the atmosphere.

Avis, L. M.↗