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Journal of Geophysical Research. Oceans

J L Bamber, A J Tedstone, M D King, I M Howat, E M Enderlin, M R van den Broeke, B Noel
The freshwater budget of the Arctic and sub-polar North Atlantic Oceans has been changing due, primarily, to increased river runoff, declining sea ice and enhanced melting of Arctic land ice. Since the mid-1990s this latter component has experienced a pronounced increase. We use a combination of satellite observations of glacier flow speed and regional climate modeling to reconstruct the land ice freshwater flux from the Greenland ice sheet and Arctic glaciers and ice caps for the period 1958-2016. The cumulative freshwater flux anomaly exceeded 6,300 ± 316 km3 by 2016...
March 2018: Journal of Geophysical Research. Oceans
Hally B Stone, Neil S Banas, Parker MacCready
The Northern California Current System experiences highly variable seasonal upwelling in addition to larger basin-scale variability, both of which can significantly affect its water chemistry. Salinity and temperature fields from a 7 year ROMS hindcast model of this region (43°N-50°N), along with extensive particle tracking, were used to study interannual variability in water properties over both the upper slope and the midshelf bottom. Variation in slope water properties was an order of magnitude smaller than on the shelf...
January 2018: Journal of Geophysical Research. Oceans
Nils Hutter, Martin Losch, Dimitris Menemenlis
Sea ice models with the traditional viscous-plastic (VP) rheology and very small horizontal grid spacing can resolve leads and deformation rates localized along Linear Kinematic Features (LKF). In a 1 km pan-Arctic sea ice-ocean simulation, the small-scale sea ice deformations are evaluated with a scaling analysis in relation to satellite observations of the Envisat Geophysical Processor System (EGPS) in the Central Arctic. A new coupled scaling analysis for data on Eulerian grids is used to determine the spatial and temporal scaling and the coupling between temporal and spatial scales...
January 2018: Journal of Geophysical Research. Oceans
Ronan McAdam, Erik van Sebille
Global surface transport in the ocean can be represented by using the observed trajectories of drifters to calculate probability distribution functions. The oceanographic applications of the Markov Chain approach to modeling include tracking of floating debris and water masses, globally and on yearly-to-centennial time scales. Here we analyze the error inherent with mapping trajectories onto a grid and the consequences for ocean transport modeling and detection of accumulation structures. A sensitivity analysis of Markov Chain parameters is performed in an idealized Stommel gyre and western boundary current as well as with observed ocean drifters, complementing previous studies on widespread floating debris accumulation...
January 2018: Journal of Geophysical Research. Oceans
Maria T Kavanaugh, Jennie E Rheuban, Kelly M A Luis, Scott C Doney
The U.S. Northeast Continental Shelf is experiencing rapid warming, with potentially profound consequences to marine ecosystems. While satellites document multiple scales of spatial and temporal variability on the surface, our understanding of the status, trends, and drivers of the benthic environmental change remains limited. We interpolated sparse benthic temperature data along the New England Shelf and upper Slope using a seasonally dynamic, regionally specific multiple linear regression model that merged in situ and remote sensing data...
December 2017: Journal of Geophysical Research. Oceans
R Somavilla, C González-Pola, J Fernández-Diaz
Ocean surface warming is commonly associated with a more stratified, less productive, and less oxygenated ocean. Such an assertion is mainly based on consistent projections of increased near-surface stratification and shallower mixed layers under global warming scenarios. However, while the observed sea surface temperature (SST) is rising at midlatitudes, the concurrent ocean record shows that stratification is not unequivocally increasing nor is MLD shoaling. We find that while SST increases at three study areas at midlatitudes, stratification both increases and decreases, and MLD deepens with enhanced deepening of winter MLDs at rates over 10 m  decade-1...
September 2017: Journal of Geophysical Research. Oceans
S Miladinova, A Stips, E Garcia-Gorriz, D Macias Moy
The current knowledge about spatial and temporal dynamics of the Black Sea's thermohaline structure is incomplete because of missing data and sparse distribution of existing measurements in space and time. This study presents 56 year continuous simulations of the Black Sea's hydrodynamics using the 3D General Estuarine Transport Model (GETM), without incorporating any relaxation toward climatological or observational data fields. This property of the model allows us to estimate independent temporal trends, in addition to resolving the spatial structure...
July 2017: Journal of Geophysical Research. Oceans
Sumit Chakraborty, Steven E Lohrenz, Kjell Gundersen
Spatial and temporal variability in photophysiological properties of phytoplankton were examined in relationship to phytoplankton community composition in the river-dominated continental margin of the northern Gulf of Mexico (NGOM). Observations made during five research cruises in the NGOM included phytoplankton photosynthetic and optical properties and associated environmental conditions and phytoplankton community structure. Distinct patterns of spatial and temporal variability in photophysiological parameters were found for waters dominated by different phytoplankton groups...
June 2017: Journal of Geophysical Research. Oceans
Greg Seroka, Travis Miles, Yi Xu, Josh Kohut, Oscar Schofield, Scott Glenn
Large uncertainty in the predicted intensity of tropical cyclones (TCs) persists compared to the steadily improving skill in the predicted TC tracks. This intensity uncertainty has its most significant implications in the coastal zone, where TC impacts to populated shorelines are greatest. Recent studies have demonstrated that rapid ahead-of-eye-center cooling of a stratified coastal ocean can have a significant impact on hurricane intensity forecasts. Using observation-validated, high-resolution ocean modeling, the stratified coastal ocean cooling processes observed in two U...
June 2017: Journal of Geophysical Research. Oceans
Chengfeng Le, John C Lehrter, Chuanmin Hu, Hugh MacIntyre, Marcus Beck
Particulate organic carbon (POC) plays an important role in coastal carbon cycling and the formation of hypoxia. Yet, coastal POC dynamics are often poorly understood due a lack of POC observations and the complexity of coastal hydrodynamic and biogeochemical processes that influence POC sources and sinks. Using a dataset of field observations and satellite ocean color products, we developed a new multiple regression algorithm to derive POC from satellite observations in two river-dominated estuaries in the northern Gulf of Mexico: the Louisiana Continental Shelf (LCS) and Mobile Bay...
January 2017: Journal of Geophysical Research. Oceans
Michael Steele, Suzanne Dickinson
In this work, we explore the seasonal relationships (i.e., the phenology) between sea ice retreat, sea surface temperature (SST), and atmospheric heat fluxes in the Pacific Sector of the Arctic Ocean, using satellite and reanalysis data. We find that where ice retreats early in most years, maximum summertime SSTs are usually warmer, relative to areas with later retreat. For any particular year, we find that anomalously early ice retreat generally leads to anomalously warm SSTs. However, this relationship is weak in the Chukchi Sea, where ocean advection plays a large role...
September 2016: Journal of Geophysical Research. Oceans
Gillian M Damerell, Karen J Heywood, Andrew F Thompson, Umberto Binetti, Jan Kaiser
This study presents the characterization of variability in temperature, salinity and oxygen concentration, including the vertical structure of the variability, in the upper 1000 m of the ocean over a full year in the northeast Atlantic. Continuously profiling ocean gliders with vertical resolution between 0.5 and 1 m provide more information on temporal variability throughout the water column than time series from moorings with sensors at a limited number of fixed depths. The heat, salt and dissolved oxygen content are quantified at each depth...
May 2016: Journal of Geophysical Research. Oceans
L A Ruiz Etcheverry, M Saraceno, A R Piola, P T Strub
We study the annual patterns and linear trend of satellite sea level anomaly (SLA) over the southwest South Atlantic continental shelf (SWACS) between 54ºS and 36ºS. Results show that south of 42°S the thermal steric effect explains nearly 100% of the annual amplitude of the SLA, while north of 42°S it explains less than 60%. This difference is due to the halosteric contribution. The annual wind variability plays a minor role over the whole continental shelf. The temporal linear trend in SLA ranges between 1 and 5 mm/yr (95% confidence level)...
April 2016: Journal of Geophysical Research. Oceans
Jianwei Wei, Zhongping Lee, Michael Ondrusek, Antonio Mannino, Maria Tzortziou, Roy Armstrong
The spectral slope of the absorption coefficient of colored dissolved and detrital material (CDM), Scdm (units: nm-1 ), is an important optical parameter for characterizing the absorption spectral shape of CDM. Although highly variable in natural waters, in most remote sensing algorithms, this slope is either kept as a constant or empirically modeled with multiband ocean color in the visible domain. In this study, we explore the potential of semianalytically retrieving Scdm with added ocean color information in the ultraviolet (UV) range between 360 and 400 nm...
March 2016: Journal of Geophysical Research. Oceans
Yevgeny Aksenov, Michael Karcher, Andrey Proshutinsky, Rüdiger Gerdes, Beverly de Cuevas, Elena Golubeva, Frank Kauker, An T Nguyen, Gennady A Platov, Martin Wadley, Eiji Watanabe, Andrew C Coward, A J George Nurser
Pacific Water (PW) enters the Arctic Ocean through Bering Strait and brings in heat, fresh water, and nutrients from the northern Bering Sea. The circulation of PW in the central Arctic Ocean is only partially understood due to the lack of observations. In this paper, pathways of PW are investigated using simulations with six state-of-the art regional and global Ocean General Circulation Models (OGCMs). In the simulations, PW is tracked by a passive tracer, released in Bering Strait. Simulated PW spreads from the Bering Strait region in three major branches...
January 2016: Journal of Geophysical Research. Oceans
Axel J Schweiger, Jinlun Zhang
Arctic sea ice drift forecasts of 6 h-9 days for the summer of 2014 are generated using the Marginal Ice Zone Modeling and Assimilation System (MIZMAS); the model is driven by 6 h atmospheric forecasts from the Climate Forecast System (CFSv2). Forecast ice drift speed is compared to drifting buoys and other observational platforms. Forecast positions are compared with actual positions 24 h-8 days since forecast. Forecast results are further compared to those from the forecasts generated using an ice velocity climatology driven by multiyear integrations of the same model...
December 2015: Journal of Geophysical Research. Oceans
Michael Steele, Wendy Ermold
Each year, the arctic sea ice edge retreats from its winter maximum extent through the Seasonal Ice Zone (SIZ) to its summer minimum extent. On some days, this retreat happens at a rapid pace, while on other days, parts of the pan-arctic ice edge hardly move for periods of days up to 1.5 weeks. We term this stationary behavior "ice edge loitering," and identify areas that are more prone to loitering than others. Generally, about 20-25% of the SIZ area experiences loitering, most often only one time at any one location during the retreat season, but sometimes two or more times...
December 2015: Journal of Geophysical Research. Oceans
I R MacDonald, O Garcia-Pineda, A Beet, S Daneshgar Asl, L Feng, G Graettinger, D French-McCay, J Holmes, C Hu, F Huffer, I Leifer, F Muller-Karger, A Solow, M Silva, G Swayze
When wind speeds are 2-10 m s(-1), reflective contrasts in the ocean surface make oil slicks visible to synthetic aperture radar (SAR) under all sky conditions. Neural network analysis of satellite SAR images quantified the magnitude and distribution of surface oil in the Gulf of Mexico from persistent, natural seeps and from the Deepwater Horizon (DWH) discharge. This analysis identified 914 natural oil seep zones across the entire Gulf of Mexico in pre-2010 data. Their ∼0.1 µm slicks covered an aggregated average of 775 km(2)...
December 2015: Journal of Geophysical Research. Oceans
Angelicque E White, Ricardo M Letelier, Amanda L Whitmire, Benedetto Barone, Robert R Bidigare, Matthew J Church, David M Karl
The particle size distribution (PSD) is a critical aspect of the oceanic ecosystem. Local variability in the PSD can be indicative of shifts in microbial community structure and reveal patterns in cell growth and loss. The PSD also plays a central role in particle export by influencing settling speed. Satellite-based models of primary productivity (PP) often rely on aspects of photophysiology that are directly related to community size structure. In an effort to better understand how variability in particle size relates to PP in an oligotrophic ecosystem, we collected laser diffraction-based depth profiles of the PSD and pigment-based classifications of phytoplankton functional types (PFTs) on an approximately monthly basis at the Hawaii Ocean Time-series Station ALOHA, in the North Pacific subtropical gyre...
November 2015: Journal of Geophysical Research. Oceans
Younjoo J Lee, Patricia A Matrai, Marjorie A M Friedrichs, Vincent S Saba, David Antoine, Mathieu Ardyna, Ichio Asanuma, Marcel Babin, Simon Bélanger, Maxime Benoît-Gagné, Emmanuel Devred, Mar Fernández-Méndez, Bernard Gentili, Toru Hirawake, Sung-Ho Kang, Takahiko Kameda, Christian Katlein, Sang H Lee, Zhongping Lee, Frédéric Mélin, Michele Scardi, Tim J Smyth, Shilin Tang, Kevin R Turpie, Kirk J Waters, Toby K Westberry
We investigated 32 net primary productivity (NPP) models by assessing skills to reproduce integrated NPP in the Arctic Ocean. The models were provided with two sources each of surface chlorophyll-a concentration (chlorophyll), photosynthetically available radiation (PAR), sea surface temperature (SST), and mixed-layer depth (MLD). The models were most sensitive to uncertainties in surface chlorophyll, generally performing better with in situ chlorophyll than with satellite-derived values. They were much less sensitive to uncertainties in PAR, SST, and MLD, possibly due to relatively narrow ranges of input data and/or relatively little difference between input data sources...
September 2015: Journal of Geophysical Research. Oceans
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