Modelling the influence of daytime distribution on the transport of two sympatric krill species (Thysanoessa raschii and Meganyctiphanes norvegica) in the Gulf of St Lawrence, eastern Canada

Abstract Maps, F., Plourde, S., Lavoie, D., McQuinn, I., and Chassé, J. 2014. Modelling the influence of daytime distribution on the transport of two sympatric krill species (Thysanoessa raschii and Meganyctiphanes norvegica) in the Gulf of St Lawrence, eastern Canada. – ICES Journal of Marine Science, 71: 282–292. The Gulf of St Lawrence (GSL) provides several species of North Atlantic baleen whale with an abundant supply of krill, dominated by Thysanoessa raschii and Meganyctiphanes norvegica. We aimed to quantify the differences in upstream advection resulting from the interaction between the circulation and the specific diel vertical migration of T. raschii and M. norvegica at the scale of the northwest GSL. We coupled a regional circulation model with Lagrangian models where the daytime depth followed specific functions of surface salinity. Our results help to explain the spatio-temporal variability in both T. raschii and M. norvegica distributions. We identified in particular spatio-temporal patterns in krill upstream transport. During summer and autumn, the upstream transport of krill is steady across Jacques Cartier Strait, limited across Honguedo Strait, and more sporadic across the Estuary mouth. We estimated that the upstream advection of krill particles across the Estuary mouth would be higher by 16–17% for the T. raschii than for the M. norvegica daytime behaviour. Our results also suggest that the advective processes operating on the adults during the productive season are not the only cause for the observed magnitude of the interannual and interspecific variability in krill abundance.

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Response of Freshwater Flux and Sea Surface Salinity to Variability of the Atlantic Warm Pool

Journal of Climate ◽

10.1175/jcli-d-12-00284.1 ◽

2013 ◽

Vol 26 (4) ◽

pp. 1249-1267 ◽

Cited By ~ 14

Author(s):

Chunzai Wang ◽

Liping Zhang ◽

Sang-Ki Lee

Keyword(s):

Central America ◽

North Atlantic ◽

Warm Pool ◽

Sea Surface ◽

Sea Surface Salinity ◽

Freshwater Flux ◽

Surface Salinity ◽

Atlantic Warm Pool ◽

Mean Circulation ◽

Circulation Dynamics

Abstract The response of freshwater flux and sea surface salinity (SSS) to the Atlantic warm pool (AWP) variations from seasonal to multidecadal time scales is investigated by using various reanalysis products and observations. All of the datasets show a consistent response for all time scales: A large (small) AWP is associated with a local freshwater gain (loss) to the ocean, less (more) moisture transport across Central America, and a local low (high) SSS. The moisture budget analysis demonstrates that the freshwater change is dominated by the atmospheric mean circulation dynamics, while the effect of thermodynamics is of secondary importance. Further decomposition points out that the contribution of the mean circulation dynamics primarily arises from its divergent part, which mainly reflects the wind divergent change in the low level as a result of SST change. In association with a large (small) AWP, warmer (colder) than normal SST over the tropical North Atlantic can induce anomalous low-level convergence (divergence), which favors anomalous ascent (decent) and thus generates more (less) precipitation. On the other hand, a large (small) AWP weakens (strengthens) the trade wind and its associated westward moisture transport to the eastern North Pacific across Central America, which also favors more (less) moisture residing in the Atlantic and hence more (less) precipitation. The results imply that variability of freshwater flux and ocean salinity in the North Atlantic associated with the AWP may have the potential to affect the Atlantic meridional overturning circulation.

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Subpolar Gyre – AMOC – Atmosphere Interactions on Multidecadal Timescales in a Version of the Kiel Climate Model

10.5194/egusphere-egu21-4608 ◽

2021 ◽

Author(s):

Jing Sun ◽

Mojib Latif ◽

Wonsun Park

Keyword(s):

North Atlantic ◽

Climate Model ◽

Deep Convection ◽

Meridional Overturning Circulation ◽

Subpolar Gyre ◽

Surface Salinity ◽

The North ◽

Ocean Coupling ◽

Meridional Overturning ◽

The North Atlantic

There is a controversy about the nature of multidecadal climate variability in the North Atlantic (NA) region, concerning the roles of ocean circulation and atmosphere-ocean coupling. Here we describe NA multidecadal variability from a version of the Kiel Climate Model, in which both subpolar gyre (SPG)-Atlantic Meridional Overturning Circulation (AMOC) and atmosphere-ocean coupling are essential. The oceanic barotropic streamfuntions, meridional overturning streamfunctions, and sea level pressure are jointly analyzed to derive the leading mode of Atlantic variability. This mode accounting for about 23.7 % of the total combined variance is oscillatory with an irregular periodicity of 25-50 years and an e-folding time of about a decade. SPG and AMOC mutually influence each other and together provide the delayed negative feedback necessary for maintaining the oscillation. An anomalously strong SPG, for example, drives higher surface salinity and density in the NA&#8217;s sinking region. In response, oceanic deep convection and AMOC intensify, which, with a time delay of about a decade, reduces SPG strength by enhancing upper-ocean heat content. The weaker gyre circulation leads to lower surface salinity and density in the sinking region, which eventually reduces deep convection and AMOC strength. There is a positive ocean-atmosphere feedback between the sea surface temperature and low-level atmospheric circulation over the Southern Greenland area, with related wind stress changes reinforcing SPG changes, thereby maintaining the (damped) multidecadal oscillation against dissipation. Stochastic surface heat-flux forcing associated with the North Atlantic Oscillation drives the eigenmode.

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Marine productivity response to Heinrich events: a model-data comparison

Climate of the Past ◽

10.5194/cp-8-1581-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 1581-1598 ◽

Cited By ~ 23

Author(s):

V. Mariotti ◽

L. Bopp ◽

A. Tagliabue ◽

M. Kageyama ◽

D. Swingedouw

Keyword(s):

North Atlantic ◽

General Circulation ◽

Circulation Model ◽

Global Ocean ◽

Biogeochemical Model ◽

Heinrich Events ◽

The North ◽

Heinrich Event ◽

The North Atlantic ◽

Marine Productivity

Abstract. Marine sediments records suggest large changes in marine productivity during glacial periods, with abrupt variations especially during the Heinrich events. Here, we study the response of marine biogeochemistry to such an event by using a biogeochemical model of the global ocean (PISCES) coupled to an ocean-atmosphere general circulation model (IPSL-CM4). We conduct a 400-yr-long transient simulation under glacial climate conditions with a freshwater forcing of 0.1 Sv applied to the North Atlantic to mimic a Heinrich event, alongside a glacial control simulation. To evaluate our numerical results, we have compiled the available marine productivity records covering Heinrich events. We find that simulated primary productivity and organic carbon export decrease globally (by 16% for both) during a Heinrich event, albeit with large regional variations. In our experiments, the North Atlantic displays a significant decrease, whereas the Southern Ocean shows an increase, in agreement with paleo-productivity reconstructions. In the Equatorial Pacific, the model simulates an increase in organic matter export production but decreased biogenic silica export. This antagonistic behaviour results from changes in relative uptake of carbon and silicic acid by diatoms. Reasonable agreement between model and data for the large-scale response to Heinrich events gives confidence in models used to predict future centennial changes in marine production. In addition, our model allows us to investigate the mechanisms behind the observed changes in the response to Heinrich events.

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More of the same: allopatric humpback whale populations share acoustic repertoire

PeerJ ◽

10.7717/peerj.5365 ◽

2018 ◽

Vol 6 ◽

pp. e5365 ◽

Cited By ~ 4

Author(s):

Michelle E.H. Fournet ◽

Lauren Jacobsen ◽

Christine M. Gabriele ◽

David K. Mellinger ◽

Holger Klinck

Keyword(s):

North Atlantic ◽

North Atlantic Ocean ◽

North Pacific Ocean ◽

Humpback Whale ◽

Humpback Whales ◽

Massachusetts Bay ◽

Baleen Whale ◽

Southeast Alaska ◽

Allopatric Populations ◽

Strong Contrast

Background Humpback whales (Megaptera novaeangliae) are a widespread, vocal baleen whale best known for producing song, a complex, repetitive, geographically distinct acoustic signal sung by males, predominantly in a breeding context. Humpback whales worldwide also produce non-song vocalizations (“calls”) throughout their migratory range, some of which are stable across generations. Methods We looked for evidence that temporally stable call types are shared by two allopatric humpback whale populations while on their northern hemisphere foraging grounds in order to test the hypothesis that some calls, in strong contrast to song, are innate within the humpback whale acoustic repertoire. Results Despite being geographically and genetically distinct populations, humpback whales in Southeast Alaska (North Pacific Ocean) share at least five call types with conspecifics in Massachusetts Bay (North Atlantic Ocean). Discussion This study is the first to identify call types shared by allopatric populations, and provides evidence that some call types may be innate.

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A modeling study of heterogeneity and surface water-groundwater interactions in the Thomas Brook catchment, Annapolis Valley (Nova Scotia, Canada)

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-6-2751-2009 ◽

2009 ◽

Vol 6 (2) ◽

pp. 2751-2793 ◽

Cited By ~ 2

Author(s):

M. J. Gauthier ◽

M. Camporese ◽

C. Rivard ◽

C. Paniconi ◽

M. Larocque

Keyword(s):

Surface Water ◽

Snow Accumulation ◽

Return Flow ◽

Eastern Canada ◽

Groundwater Levels ◽

The North ◽

Spatio Temporal ◽

Geological Complexity ◽

Annapolis Valley ◽

Response Variables

Abstract. A modelling study of the impacts of subsurface heterogeneity on the hydrologic response of an 8 km2 catchment in the Annapolis Valley (Eastern Canada) is reported. The study is focused in particular on the hydraulic connection and interactions between surface water and groundwater. A coupled (1-D surface/3-D subsurface) numerical model is used to investigate, for a range of scenarios, the spatio-temporal patterns of response variables such as return flow, recharge, groundwater levels, surface saturation, and streamflow. Eight scenarios of increasing geological complexity are simulated, introducing at each step more realistic representations of the geological strata and corresponding hydraulic properties. In a ninth scenario the effects of snow accumulation and snowmelt are also considered. The results show that response variables and significant features of the catchment (e.g., springs) can be adequately reproduced using a representation of the geology and model parameter values that are based on targeted fieldwork and existing databases, and that reflect to a sufficient degree the geological and hydrological complexity of the study area. The hydraulic conductivity values of the thin surficial sediment cover (especially till) and of the North Mountain basalts emerge as key elements of the basin's heterogeneity for properly capturing the overall catchment response.

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Diagnosing transit times on the northwestern North Atlantic continental shelf

10.5194/os-2018-60 ◽

2018 ◽

Author(s):

Krysten Rutherford ◽

Katja Fennel

Keyword(s):

North Atlantic ◽

Gulf Of Maine ◽

Circulation Model ◽

Shelf Break ◽

Genetic Connectivity ◽

Western Boundary ◽

Coastal Current ◽

Scotian Shelf ◽

Grand Banks ◽

Transit Times

Abstract. The circulation in the northwestern North Atlantic Ocean is highly complex, characterized by the confluence of two major western boundary current systems and several shelf currents. Here we present the first comprehensive analysis of transport paths and timescales for the northwestern North Atlantic shelf, which is useful for estimating ventilation rates, describing circulation and mixing, characterizing the composition of water masses with respect to different source regions, and elucidating rates and patterns of biogeochemical processing, species dispersal and genetic connectivity. Our analysis uses dye and age tracers within a high-resolution circulation model of the region, divided into 9 sub-regions, to diagnose retention times, transport pathways, and transit times. Retention times are shortest on the Scotian Shelf (~ 3 months) where the inshore and shelf-break branches of the coastal current system result in high along-shelf transport to the southwest. Larger retention times are simulated on the Grand Banks (~ 4 months), in the Gulf of St. Lawrence (~ 12 months) and the Gulf of Maine (~ 6 months). Source water analysis shows that Scotian Shelf water is primarily comprised of waters from the Grand Banks and Gulf of St. Lawrence, with varying composition across the shelf. Contributions from the Gulf of St. Lawrence are larger at near-shore locations, whereas locations near the shelf break have larger contributions from the Grand Banks and slope waters. Waters from the deep slope have little connectivity with the shelf, because the shelf-break current inhibits transport across the shelf break. Grand Banks and Gulf of St. Lawrence waters are therefore dominant controls on biogeochemical properties, and on setting and sustaining planktonic communities on the Scotian Shelf.

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A global eddying hindcast ocean simulation with OFES2

Geoscientific Model Development ◽

10.5194/gmd-13-3319-2020 ◽

2020 ◽

Vol 13 (7) ◽

pp. 3319-3336 ◽

Cited By ~ 1

Author(s):

Hideharu Sasaki ◽

Shinichiro Kida ◽

Ryo Furue ◽

Hidenori Aiki ◽

Nobumasa Komori ◽

...

Keyword(s):

General Circulation ◽

Circulation Model ◽

Ocean General Circulation Model ◽

Sea Surface ◽

Sea Surface Salinity ◽

Tidal Mixing ◽

Surface Salinity ◽

Previous Version ◽

Spatiotemporal Scales ◽

The Kuroshio

Abstract. A quasi-global eddying ocean hindcast simulation using a new version of our model, called OFES2 (Ocean General Circulation Model for the Earth Simulator version 2), was conducted to overcome several issues with unrealistic properties in its previous version, OFES. This paper describes the model and the simulated oceanic fields in OFES2 compared with OFES and also observed data. OFES2 includes a sea-ice model and a tidal mixing scheme, is forced by a newly created surface atmospheric dataset called JRA55-do, and simulated the oceanic fields from 1958 to 2016. We found several improvements in OFES2 over OFES: smaller biases in the global sea surface temperature and sea surface salinity as well as the water mass properties in the Indonesian and Arabian seas. The time series of the Niño3.4 and Indian Ocean Dipole (IOD) indexes are somewhat better in OFES2 than in OFES. Unlike the previous version, OFES2 reproduces more realistic anomalously low sea surface temperatures during a positive IOD event. One possible cause of these improvements in El Niño and IOD events is the replacement of the atmospheric dataset. On the other hand, several issues remained unrealistic, such as the pathways of the Kuroshio and Gulf Stream and the unrealistic spreading of salty Mediterranean overflow. Given the worldwide use of the previous version and the improvements presented here, the output from OFES2 will be useful in studying various oceanic phenomena with broad spatiotemporal scales.

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The stability of the North Atlantic thermohaline circulation in a coupled ocean-atmosphere general circulation model

Climate Dynamics ◽

10.1007/s003820050169 ◽

1997 ◽

Vol 13 (5) ◽

pp. 325-347 ◽

Cited By ~ 199

Author(s):

A. Schiller ◽

U. Mikolajewicz ◽

R. Voss

Keyword(s):

North Atlantic ◽

General Circulation ◽

Thermohaline Circulation ◽

Circulation Model ◽

The North ◽

Ocean Atmosphere ◽

Atmosphere General Circulation Model ◽

The North Atlantic ◽

Atlantic Thermohaline Circulation ◽

The Stability

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Mapping Spatio-Temporal Variability in NAO Rainfall Signatures

10.5194/egusphere-egu21-10982 ◽

2021 ◽

Author(s):

Harry West ◽

Nevil Quinn ◽

Michael Horswell

Keyword(s):

Spatial Pattern ◽

North Atlantic ◽

Temporal Variability ◽

Reliable Estimate ◽

Jet Stream ◽

Temporal Consistency ◽

North West ◽

The North ◽

Cold Spots ◽

Spatio Temporal

The North Atlantic Oscillation (NAO) is often cited as the primary atmospheric-oceanic circulation or teleconnection influencing regional climate in Great Britain. As our ability to predict the NAO several months in advance improves, it is important that we also continue to develop our spatial and temporal understanding of the rainfall signatures which the circulation produces.We present a novel application of spatial statistics to explore variability in monthly NAO rainfall signatures using a 5km gridded monthly Standardised Precipitation Index (SPI) dataset. We first use the Getis-Ord Gi* statistic to map spatially significant hot and cold spots (clusters of high/wet and low/dry SPI values) in average monthly rainfall signatures under NAO Positive and Negative conditions over the period 1900-2015. We then look across the record and explore the temporal variability in these signatures, in other words how often a location is in a significant spatial hot/cold spot (high/low SPI) at a monthly scale under NAO Positive/Negative conditions.The two phases of the NAO are typically more distinctive in the winter months, with stronger and more variable NAO Index values. The average monthly SPI analysis reveals a north-west/south-east &#8216;spatial divide&#8217; in rainfall response. NAO Positive phases result in a southerly North Atlantic Jet Stream bringing warm and wet conditions from the tropics, increasing rainfall particularly in the north-western regions. However, under NAO Negative phases which result in a northerly Jet Stream, much drier conditions in the north-west prevail. Meanwhile in the south-eastern regions under both NAO phases a weaker and opposite wet/dry signal is observed. This north-west/south-east &#8216;spatial divide&#8217; is marked by the location of spatially extensive hot/cold spots. The Getis-Ord Gi* result identifies that the spatial pattern we detect in average winter rainfall is statistically significant. Looking across the record, this NW/SE opposing response appears to have a relatively high degree of spatio-temporal consistency. This suggests that there is a high probability that NAO Positive and Negative phases will result in this NW/SE statistically significant spatial pattern.Even though the phases of the NAO in the summer months are less distinctive they still produce rainfall responses which are evident in the monthly average SPI. However, the spatiality in wet/dry conditions is more homogenous across the country. In other words the &#8216;spatial divide&#8217; observed in winter is diluted in summer. As a result, the occurrence of significant hot/cold spots is more variable in space and time.Our analysis demonstrates a novel application of the Getis-Ord Gi* statistic which allows for spatially significant patterns in the monthly SPI data to be mapped for each NAO phase. In winter months particularly, this analysis reveals statistically significant opposing rainfall responses, which appear to have long-term spatio-temporal consistency. This is important because as winter NAO forecasting skill improves, the findings of our research enable a more spatially reliable estimate of the likely impacts of NAO-influenced rainfall distribution.

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A global decadal mode in a high-end climate model and in observations: Any connection to the solar cycle?

10.5194/egusphere-egu21-4961 ◽

2021 ◽

Author(s):

Michael Ghil ◽

Yizhak Feliks ◽

Justin Small

Keyword(s):

Solar Cycle ◽

Sea Level ◽

North Atlantic ◽

Climate Model ◽

Decadal Variability ◽

Singular Spectrum Analysis ◽

Coupled System ◽

The North ◽

Spatio Temporal ◽

Decadal Mode

The present work addresses two persistent quandaries of the climate sciences: (i) the existence of global oscillatory modes in the coupled ocean&#8211;atmosphere system; and (ii) solar effects on this coupled system. Interannual oscillatory modes, atmospheric and oceanic, are present in several large regions of the globe. We examine here interannual-to-decadal variability over the entire globe in the Community Earth System Model (CESM) and in the NCEP-NCAR reanalysis, and apply multichannel singular spectrum analysis (MSSA) to these two datasets.In the fully coupled CESM1.1 model, with its resolution of 0.1 &#215; 0.1 degrees in the ocean and 0.25 &#215; 0.25 degrees in the atmosphere, the &#64257;elds analyzed are surface temperatures, sea level pressures and&#160; the 200-hPa geopotential. The simulation is 100-yr long and the last 66 yr are used in the analysis. The two statistically signi&#64257;cant periodicities in this IPCC-class model are 11 and 3.4 yr.In the reanalysis, the &#64257;elds of sea level pressure and of 200-hPa geopotential are analyzed at its resolution of 2.5 &#215; 2.5 degrees over the 68-yr interval 1949&#8211;2016. Oscillations with periods of 12 and 3.6 yr are found to be statistically signi&#64257;cant in this dataset. The spatio-temporal patterns&#160; of the oscillations in the two datasets are quite similar. The spatial pattern of these&#160; global oscillations over the North Paci&#64257;c and North Atlantic resemble the Paci&#64257;c Decadal Oscillation and the interannual variability found in the western North Atlantic, respectively.The two global modes, with their 11&#8211;12-yr and 3.4&#8211;3.6-yr periodicities, are quite robust, suggesting potential contributions of both to predictability at 1&#8211;3-yr horizons. On the other hand, the CESM run has no year-to-year changes in the prescribed insolation, excluding any role of the solar cycle in the model&#8217;s 11-yr mode. The solar cycle is present, however, in the reanalysis, since it is present in nature and hence it does affect the observations. We speculate, therefore, that regional oscillations &#8212; with their distinct near-periodicities and spatial patterns &#8212; are synchronized&#160; over the globe, thus yielding both the global oscillatory modes found in CESM. In nature, the decadal mode could be further synchronized with the solar cycle, but that does not seem to be the case, given the slight difference in period &#8212; 12 yr for the reanalysis and 11 yr for the solar cycle, which makes them drift in and out of phase.The work&#8217;s tentative conclusion is, therefore: (i) yes, there are global oscillatory modes in the climate system, especially a decadal mode; but (ii) no, this mode has little or nothing to do with the solar cycle.

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