The Impact of Lateral Boundary Conditions and Horizontal Resolution on North Atlantic Water Mass Transformations and Pathways in an Isopycnic Coordinate Ocean Model

Surface sediment samples (n = 10), collected between Spitzbergen and Greenland, and two cores raised east (C04) and west (C16) from Fram Strait were analyzed for their chemical and isotopic (Pb) compositions to trace the source of sediments and water masses exchanging between the Arctic and the North Atlantic oceans. In surface sediments, variable major and trace element concentrations suggest variations in both the mineralogy (carbonate and quartz dilution of other silicate minerals) and source regions of detrital supplies, based on Th/Zr and, to a lesser extent, on Th/U ratios. Each core site shows specific but nearly constant Th/Zr ratios, indicating homogeneous source supplies. At both core sites, Pb concentrations and isotopic compositions display similar patterns: homogeneous low Pb and radiogenic crustal signals below 5–10 cm, contrasting with high Pb and less radiogenic anthropogenic inputs at core-tops. However, the differing pre-anthropogenic Pb isotopic ratios in C04 and C16 confirm the involvement of distinct source supplies east and west of Fram Strait. We suggest that this isotopic specificity is mainly owing to inputs of material carried from northwestern Europe by the North Atlantic water mass and from the Laptev Sea by the Transpolar Drift, respectively. Some material from the Greenland margin and possibly from the North Atlantic Ocean may reach this zone as well. Sediments from the western Arctic are not significantly transported into the Fram Strait area, suggesting that the Canadian and the Eurasian basins remained decoupled, at least during the time span of the cored sediments (∼2000 years).

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Diagnostic study of the influence of lateral boundary conditions for the REMO RCM simulations over the Carpathian Basin

Advances in Science and Research ◽

10.5194/asr-6-87-2011 ◽

2011 ◽

Vol 6 (1) ◽

pp. 87-94

Author(s):

G. Szépszó

Keyword(s):

Boundary Conditions ◽

Climate Model ◽

Global Climate Model ◽

Analysis Data ◽

Horizontal Resolution ◽

Carpathian Basin ◽

Diagnostic Study ◽

Lateral Boundary ◽

Lateral Boundary Conditions ◽

The Impact

Abstract. At the Hungarian Meteorological Service, two experiments were accomplished with the REMO5.0 regional climate model: (1) a simulation of a past period from 1961 to 2000, driven by the ECMWF ERA40 re-analysis data, and (2) a transient run from 1951 to 2100 driven by the ECHAM5/MPI-OM global coupled atmosphere-ocean model using SRES A1B forcing. The integration domain covers continental Europe with 25 km horizontal resolution in both experiments. Present article is dedicated to the investigation of the simulation results for the past period. The results for 1961–1990 were compared on the one hand with observations, and on the other hand, with each other and the corresponding global fields in order to assess the impact of the different lateral boundary conditions on the results focusing on the area of our interest, i.e., Hungary. The evaluation indicated that the re-analysis driven experiment provides warm and in summer dry past climate over the Carpathian Basin, whereas lower temperature and higher precipitation values are obtained when the lateral boundary information is derived from a global climate model. Based on the validation, it is concluded that the temperature characteristics in the simulation-driven case outperformed the experiment forced by quasi-perfect (i.e., re-analysis) data, however, similar apparent conclusion cannot be drawn for precipitation. This paper is undertaking to give deeper insight into the details and possible reasons for these outcomes.

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Exploratory analyses of trichlorofluoromethane (F-11) in North Atlantic water columns

Geophysical Research Letters ◽

10.1029/gl005i008p00645 ◽

1978 ◽

Vol 5 (8) ◽

pp. 645-648 ◽

Cited By ~ 21

Author(s):

Paul M. Hammer ◽

J. M. Hayes ◽

W. J. Jenkins ◽

R. B. Gagosian

Keyword(s):

North Atlantic ◽

Atlantic Water ◽

Water Columns ◽

North Atlantic Water

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Impacts of Oceanic Preexisting Conditions on Predictions of Typhoon Hai-Tang in 2005

Advances in Meteorology ◽

10.1155/2010/756071 ◽

2010 ◽

Vol 2010 ◽

pp. 1-15 ◽

Cited By ~ 7

Author(s):

Akiyoshi Wada ◽

Norihisa Usui

Keyword(s):

Mixed Layer ◽

Initial Conditions ◽

Horizontal Resolution ◽

Ocean Model ◽

Central Pressure ◽

Surface Cooling ◽

Heat Potential ◽

Spiral Rainbands ◽

The Impact ◽

Preexisting Conditions

We investigated the impact of variations in oceanic preexisting conditions on predictions of Typhoon Hai-Tang (2005) by using a coupled atmosphere-ocean model with 6-km horizontal resolution and providing the oceanic initial conditions on 12 July from 1997 to 2005 to the model. Variations in oceanic preexisting conditions caused variation in predicted central pressure of nearly 18 hPa at 72 h, whereas sea-surface cooling (SSC) induced by Hai-Tang caused a predicted central pressure difference of about 40 hPa. Warm-core oceanic eddies up to a few hundred kilometers across and a deep mixed layer climatologically distributed in the western North Pacific led to high mixed-layer heat potential, which increased latent heat flux, water vapor, and liquid water contents around Hai-Tang's center. These increases were closely associated with Hai-Tang's intensification. SSC negatively affected the eyewall, whereas variations in oceanic preexisting conditions remarkably affected spiral rainbands and the magnitude of SSC.

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Long-term ventilation changes of Subpolar Mode Waters in the North Atlantic Ocean and its impact on the oxygen distribution

10.5194/egusphere-egu21-847 ◽

2021 ◽

Author(s):

Ilaria Stendardo ◽

Bruno Buongiorno Nardelli ◽

Sara Durante

Keyword(s):

Atlantic Ocean ◽

North Atlantic ◽

North Atlantic Ocean ◽

Horizontal Resolution ◽

Late Winter ◽

Mode Water ◽

Mode Waters ◽

The North ◽

The North Atlantic ◽

The Impact

<p>In the subpolar North Atlantic Ocean, Subpolar Mode Waters (SPMWs) are formed during late winter convection following the cyclonic circulation of the subpolar gyre. SPMWs participate in the upper flow of the Atlantic overturning circulation (AMOC) and provide much of the water that is eventually transformed into several components of the North Atlantic deep water (NADW), the cold, deep part of the AMOC. In a warming climate, an increase in upper ocean stratification is expected to lead to a reduced ventilation and a loss of oxygen. Thus, understanding how mode waters are affected by ventilation changes will help us to better understand the variability in the AMOC. In particular, we would like to address how the volume occupied by SPMWs has varied over the last decades due to ventilation changes, and what are the aspects driving the subpolar mode water formation, their interannual variations as well as the impact of the variability in the mixing and subduction and vertical dynamics on ocean deoxygenation. For this purpose, we use two observation-based 3D products from Copernicus Marine Service (CMEMS), the ARMOR3D and the OMEGA3D datasets. The first consists of 3D temperature and salinity fields, from the surface to 1500 m depth, available weekly over a regular grid at 1/4&#176; horizontal resolution from 1993 to present. The second consists of observation-based quasi-geostrophic vertical and horizontal ocean currents with the same temporal and spatial resolution as ARMOR3D.</p>

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Greenland melting signatures in model simulations and oceanic observations

10.5194/egusphere-egu21-8225 ◽

2021 ◽

Author(s):

Sophie Stolzenberger ◽

Roelof Rietbroek ◽

Claudia Wekerle ◽

Bernd Uebbing ◽

Jürgen Kusche

Keyword(s):

North Atlantic ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ocean Model ◽

Freshwater Flux ◽

Model Simulations ◽

The North ◽

Sea Level Anomalies ◽

The North Atlantic ◽

The Impact

<p>The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.</p>

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Wind-driven transport of fresh shelf water into the upper 30 m of the Labrador Sea

Ocean Science ◽

10.5194/os-14-1247-2018 ◽

2018 ◽

Vol 14 (5) ◽

pp. 1247-1264 ◽

Cited By ~ 8

Author(s):

Lena M. Schulze Chretien ◽

Eleanor Frajka-Williams

Keyword(s):

North Atlantic ◽

Surface Waters ◽

Deep Convection ◽

Greenland Ice Sheet ◽

Ocean Model ◽

Meridional Overturning Circulation ◽

Ekman Transport ◽

Labrador Sea ◽

The North ◽

The Impact

Abstract. The Labrador Sea is one of a small number of deep convection sites in the North Atlantic that contribute to the meridional overturning circulation. Buoyancy is lost from surface waters during winter, allowing the formation of dense deep water. During the last few decades, mass loss from the Greenland ice sheet has accelerated, releasing freshwater into the high-latitude North Atlantic. This and the enhanced Arctic freshwater export in recent years have the potential to add buoyancy to surface waters, slowing or suppressing convection in the Labrador Sea. However, the impact of freshwater on convection is dependent on whether or not it can escape the shallow, topographically trapped boundary currents encircling the Labrador Sea. Previous studies have estimated the transport of freshwater into the central Labrador Sea by focusing on the role of eddies. Here, we use a Lagrangian approach by tracking particles in a global, eddy-permitting (1/12∘) ocean model to examine where and when freshwater in the surface 30 m enters the Labrador Sea basin. We find that 60 % of the total freshwater in the top 100 m enters the basin in the top 30 m along the eastern side. The year-to-year variability in freshwater transport from the shelves to the central Labrador Sea, as found by the model trajectories in the top 30 m, is dominated by wind-driven Ekman transport rather than eddies transporting freshwater into the basin along the northeast.

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Paleoenvironments along the Eastern Laurentide Ice Sheet Margin and Timing of the Last Ice Maximum and Retreat

Géographie physique et Quaternaire ◽

10.7202/032682ar ◽

2008 ◽

Vol 41 (2) ◽

pp. 265-277 ◽

Cited By ~ 18

Author(s):

Anne de Vernal ◽

Claude Hillaire-Marcel

Keyword(s):

Late Pleistocene ◽

North Atlantic ◽

Environmental Changes ◽

Atlantic Water ◽

Polar Front ◽

Water Masses ◽

Labrador Sea ◽

Eastern Canada ◽

North Atlantic Water ◽

Late Wisconsinan

ABSTRACT Palynological and isotopic analysis in a few deep-sea cores from the Labrador Sea reveals strong environmental changes related to the Late Pleistocene glacial fluctuations over eastern Canada. On the whole, the Labrador Sea was characterized by strong exchanges between North Atlantic water masses, Arctic outflows, and meltwater discharges from Laurentide, Greenland and lnuitian ice sheets. The penetration of temperate Atlantic waters persisted throughout most of the Late Pleistocene, with a brief interruption during the Late Wisconsinan. During this glacial substage, a slight but continuous meltwater runoff from the Laurentide ice margins grounded on the northern Labrador Shelf is indicated by relatively low 18O values and low-salinity (< 30‰) dinocyst assemblages. The calving of the ice margin, the melwater outflow and the subsequent dilution of surface waters offshore Labrador probably contributed to the dispersal of floating ice and, consequently, to a southward displacement of the polar front restraining the penetration of North Atlantic waters into the Labrador Sea. The advection of southern air masses along the Laurentide ice margins, shown by pollen assemblages, was favourable to abundant precipitation and therefore, high ice accumulation rates, especially over northern Labrador during the Late Wisconsinan. The déglaciation is marked by a brief, but significant, melting event of northern Laurentide ice shortly after 17 ka. The main glacial retreat occurred after ca. 11 ka. It allowed restoration of WSW-ENE atmospheric trajectories, increased phytoplanktonic productivity, and penetration of North Atlantic water masses into the Labrador Sea.

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Estimating the Uncertainty in a Regional Climate Model Related to Initial and Lateral Boundary Conditions

Journal of Climate ◽

10.1175/jcli-3293.1 ◽

2005 ◽

Vol 18 (7) ◽

pp. 917-933 ◽

Cited By ~ 72

Author(s):

Wanli Wu ◽

Amanda H. Lynch ◽

Aaron Rivers

Keyword(s):

Boundary Conditions ◽

Climate Model ◽

Initial Conditions ◽

Climate Modeling ◽

Regional Climate ◽

Regional Climate Modeling ◽

Regional Model ◽

Lateral Boundary ◽

Lateral Boundary Conditions ◽

The Impact

Abstract There is a growing demand for regional-scale climate predictions and assessments. Quantifying the impacts of uncertainty in initial conditions and lateral boundary forcing data on regional model simulations can potentially add value to the usefulness of regional climate modeling. Results from a regional model depend on the realism of the driving data from either global model outputs or global analyses; therefore, any biases in the driving data will be carried through to the regional model. This study used four popular global analyses and achieved 16 driving datasets by using different interpolation procedures. The spread of the 16 datasets represents a possible range of driving data based on analyses to the regional model. This spread is smaller than typically associated with global climate model realizations of the Arctic climate. Three groups of 16 realizations were conducted using the fifth-generation Pennsylvania State University–National Center for Atmospheric Research (PSU–NCAR) Mesoscale Model (MM5) in an Arctic domain, varying both initial and lateral boundary conditions, varying lateral boundary forcing only, and varying initial conditions only. The response of monthly mean atmospheric states to the variations in initial and lateral driving data was investigated. Uncertainty in the regional model is induced by the interaction between biases from different sources. Because of the nonlinearity of the problem, contributions from initial and lateral boundary conditions are not additive. For monthly mean atmospheric states, biases in lateral boundary conditions generally contribute more to the overall uncertainty than biases in the initial conditions. The impact of initial condition variations decreases with the simulation length while the impact of variations in lateral boundary forcing shows no clear trend. This suggests that the representativeness of the lateral boundary forcing plays a critical role in long-term regional climate modeling. The extent of impact of the driving data uncertainties on regional climate modeling is variable dependent. For some sensitive variables (e.g., precipitation, boundary layer height), even the interior of the model may be significantly affected.

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