Orographic Distillation and spatio‐temporal variations of stable isotopes in precipitation in the North Atlantic

2018 ◽  
Author(s):  
Paulo Antunes ◽  
David F. Boutt ◽  
Francisco C. Rodrigues
Keyword(s):  
Stable Isotopes ◽  
North Atlantic ◽  
Temporal Variations ◽  
The North ◽  
The North Atlantic ◽  
Spatio Temporal

scholarly journals Methodological approaches to determining the marine radiocarbon reservoir effect

2005 ◽  
Vol 29 (4) ◽  
pp. 532-547 ◽  
Author(s):  
Philippa Ascough ◽  
Gordon Cook ◽  
Andrew Dugmore
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Temporal Variations ◽  
Oceanic Circulation ◽  
Terrestrial Environment ◽  
Reservoir Effect ◽  
The North ◽  
Quantitative Measurements ◽  
14C Age ◽  
The North Atlantic

The marine radiocarbon reservoir effect is an offset in 14C age between contemporaneous organisms from the terrestrial environment and organisms that derive their carbon from the marine environment. Quantification of this effect is of crucial importance for correct calibration of the 14C ages of marine-influenced samples to the calendrical timescale. This is fundamental to the construction of archaeological and palaeoenvironmental chronologies when such samples are employed in 14C analysis. Quantitative measurements of temporal variations in regional marine reservoir ages also have the potential to be used as a measure of process changes within Earth surface systems, due to their link with climatic and oceanic changes. The various approaches to quantification of the marine radiocarbon reservoir effect are assessed, focusing particularly on the North Atlantic Ocean. Currently, the global average marine reservoir age of surface waters, R(t), is c. 400 radiocarbon years; however, regional values deviate from this as a function of climate and oceanic circulation systems. These local deviations from R(t) are expressed as +R values. Hence, polar waters exhibit greater reservoir ages (δR = c. +400 to +800 14C y) than equatorial waters (δR = c. 0 14C y). Observed temporal variations in δR appear to reflect climatic and oceanographic changes. We assess three approaches to quantification of marine reservoir effects using known age samples (from museum collections), tephra isochrones (present onshore/offshore) and paired marine/terrestrial samples (from the same context in, for example, archaeological sites). The strengths and limitations of these approaches are evaluated using examples from the North Atlantic region. It is proposed that, with a suitable protocol, accelerator mass spectrometry (AMS) measurements on paired, short-lived, single entity marine and terrestrial samples from archaeological deposits is the most promising approach to constraining changes over at least the last 5 ky BP.

scholarly journals The response of Iberian rivers to the North Atlantic Oscillation

2011 ◽  
Vol 8 (3) ◽  
pp. 4459-4493 ◽  
Author(s):  
J. Lorenzo-Lacruz ◽  
S. M. Vicente-Serrano ◽  
J. I. López-Moreno ◽  
J. C. González-Hidalgo ◽  
E. Morán-Tejeda
Keyword(s):  
Water Resources ◽  
North Atlantic Oscillation ◽  
Iberian Peninsula ◽  
North Atlantic ◽  
The North ◽  
Surface Water Resources ◽  
The North Atlantic ◽  
Spatio Temporal ◽  
The North Atlantic Oscillation ◽  
Iberian Rivers

Abstract. In this study we analyzed the influence of the North Atlantic Oscillation (NAO) on the streamflow in 187 sub-basins of the Iberian Peninsula. Monthly and one-month lagged correlations were conducted to assess the spatio-temporal extent of the NAO influence on Iberian river discharges. Analysis of the persistence of the winter NAO throughout the year was also undertaken, together with analysis of streamflow anomalies during positive and negative NAO phases. Moving-window correlation analyses were conducted to assess potential changes in the temporal evolution of the NAO influence on Iberian streamflows. The results show that the NAO has a large impact on surface water resources throughout the Iberian Peninsula during winter, and in the Atlantic watershed during autumn. We showed that water resources management and snowmelt are causing the persistent dependence of streamflows on the previous winter NAO. We found that strongly positive streamflow anomalies occurred during winter, especially in the Atlantic watershed, and provide evidence of non-stationarity and spatial variability in the NAO influence on Iberian water resources.

scholarly journals Earlier colony arrival but no trend in hatching timing in two congeneric seabirds ( Uria spp.) across the North Atlantic

2019 ◽  
Vol 15 (10) ◽  
pp. 20190634 ◽  
Author(s):  
Benjamin Merkel ◽  
Sébastien Descamps ◽  
Nigel G. Yoccoz ◽  
Jóhannis Danielsen ◽  
Francis Daunt ◽  
...  
Keyword(s):  
North Atlantic ◽  
Global Analysis ◽  
Breeding Site ◽  
Egg Laying ◽  
Breeding Phenology ◽  
Arrival Date ◽  
Temperature Changes ◽  
The North ◽  
The North Atlantic ◽  
Spatio Temporal

A global analysis recently showed that seabird breeding phenology (as the timing of egg-laying and hatching) does not, on average, respond to temperature changes or advance with time (Keogan et al. 2018 Nat. Clim. Change 8 , 313–318). This group, the most threatened of all birds, is therefore prone to spatio-temporal mismatches with their food resources. Yet, other aspects of the breeding phenology may also have a marked influence on breeding success, such as the arrival date of adults at the breeding site following winter migration. Here, we used a large tracking dataset of two congeneric seabirds breeding in 14 colonies across 18° latitudes, to show that arrival date at the colony was highly variable between colonies and species (ranging 80 days) and advanced 1.4 days/year while timing of egg-laying remained unchanged, resulting in an increasing pre-laying duration between 2009 and 2018. Thus, we demonstrate that potentially not all components of seabird breeding phenology are insensitive to changing environmental conditions.

Overview of nutrient cycling in the sub-Arctic Atlantic regions: insights from nitrate & silicon isotopes

2021 ◽  
Author(s):  
Margot Debyser ◽  
Robyn Tuerena ◽  
Raja Ganeshram ◽  
Laetitia Pichevin
Keyword(s):  
Stable Isotopes ◽  
Nutrient Cycling ◽  
Primary Production ◽  
Silicic Acid ◽  
North Atlantic ◽  
Nutrient Budget ◽  
The Arctic ◽  
Silicon Isotopes ◽  
The North ◽  
The North Atlantic

<p>The environmental consequences of rapid climate change are already becoming apparent in the Arctic. Polar amplification has led to major loss of sea ice, increasing freshwater run-off and a poleward intrusion of Atlantic waters, thereby affecting biogeochemical cycles. Additionally, while primary production in the Arctic has increased by >50% over the last two decades (Lewis et al., 2020), it is still unclear whether Arctic nutrient budgets can sustain this increase on the long-term. Increased primary production in the central Arctic has the potential to reduce nutrient concentrations of Arctic outflow waters and modify their nutrient ratios, having consequences for the Atlantic nutrient budget.</p><p>Primary production in the Arctic is principally nitrogen-limited as a result of benthic denitrification on Arctic shelves. This is contrasted by silicon limitation in water masses originating from the Atlantic basin. To untangle the complexities of dual nutrient limitation and to gain insights into the role of Arctic outflows in controlling nutrient export to the North Atlantic, we examine the cycling of both major nutrients, nitrate and silicic acid, in key Arctic seas and straits. Using stable isotopes of dissolved nitrate and silicic acid, we provide new insights into the  mechanisms and factors that control nutrient cycling in the Arctic Ocean: nutrient origins, transformation during transport, as well as the relative contribution of primary production, remineralisation and regeneration to water column inventories.</p><p>In this study, measurements of nutrient stoichiometry and stable isotopes of dissolved nitrate and silicic acid profiles are presented across the Fram Strait, Labrador Sea (AR7W transect), and the Iceland Basin and Irminger Sea (the Extended Ellett line and the OSNAP-East program). The measured variability in nutrient isotope signatures across the Arctic gateways brings to light the contribution of Arctic-sourced freshwater to the North Atlantic and its potential impact to the North Atlantic nutrient budget with future changes to primary production in these key regions.</p>

scholarly journals Marine biological shifts and climate

2014 ◽  
Vol 281 (1783) ◽  
pp. 20133350 ◽  
Author(s):  
Grégory Beaugrand ◽  
Eric Goberville ◽  
Christophe Luczak ◽  
Richard R Kirby
Keyword(s):  
Climate Change ◽  
North Atlantic ◽  
Significant Proportion ◽  
Calanus Finmarchicus ◽  
The North ◽  
The North Sea ◽  
Community Shifts ◽  
The North Atlantic ◽  
Spatio Temporal

Phenological, biogeographic and community shifts are among the reported responses of marine ecosystems and their species to climate change. However, despite both the profound consequences for ecosystem functioning and services, our understanding of the root causes underlying these biological changes remains rudimentary. Here, we show that a significant proportion of the responses of species and communities to climate change are deterministic at some emergent spatio-temporal scales, enabling testable predictions and more accurate projections of future changes. We propose a theory based on the concept of the ecological niche to connect phenological, biogeographic and long-term community shifts. The theory explains approximately 70% of the phenological and biogeographic shifts of a key zooplankton Calanus finmarchicus in the North Atlantic and approximately 56% of the long-term shifts in copepods observed in the North Sea during the period 1958–2009.

Mapping Wet-Dry Signatures of the North Atlantic Oscillation (NAO) in British Catchments

2020 ◽  
Author(s):  
Harry West ◽  
Nevil Quinn ◽  
Michael Horswell
Keyword(s):  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Temporal Analysis ◽  
Precipitation Patterns ◽  
The North ◽  
Standardised Precipitation Index ◽  
The North Atlantic ◽  
Spatio Temporal ◽  
The North Atlantic Oscillation ◽  
The Relationship

<p>The North Atlantic Oscillation (NAO) is one of the primary atmospheric circulations which influence weather patterns in Great Britain. Its two phases (either positive or negative depending on differences in sea level pressure) result in characteristic precipitation patterns, the effects of which cascade down to signatures in streamflow. However, in relation to streamflow response to the NAO, these studies have been spatio-temporally limited as they have been undertaken using a small number of measurement sites with relatively short records.</p><p>The release of new historic datasets from the UK Centre for Ecology and Hydrology (CEH) provides a new opportunity to undertake a broad spatio-temporal analysis of the relationship between NAO and streamflow. This research used reconstructed daily flows for 291 catchments and the associated Standardised Streamflow Index (SSI) to explore the relationship between the North Atlantic Oscillation Index (NAOI) for the period January 1900-November 2015. Spearman correlations were calculated at monthly intervals between the NAOI and SSI (with a 1-month accumulation period), and the historic flows dataset was used to explore the variability in flows across the catchments under NAO+ and NAO- phases.</p><p>This analysis revealed distinct wet and dry spatio-temporal signatures in streamflow. The winter months are characterised by a north-west and south-east divide in this relationship; catchments in the northern and western regions show strong positive correlations between the NAOI and SSI and NAO+ is associated with higher than normal flows in many north-western catchments, and vice versa under NAO-. While catchments in the south-eastern and central regions are negatively correlated and therefore show and opposite wet-dry response. However, during the summer months, while there are some wet-dry signatures under NAO positive/negative phases - the reverse to that seen in winter, almost all catchments show weak NAOI-SSI negative correlation values. </p><p>Finally, we compare the wet-dry responses to the NAO observed in streamflow to NAO-precipitation patterns, measured via correlations between the NAOI and Standardised Precipitation Index with a 1-month accumulation period over the same study period. The two sets of correlations (NAO-SPI and NAO-SSI) were analysed for spatio-temporal similarity through a Geographically Weighted Regression (GWR) analysis and a space-time clustering analysis. This revealed that in winter, as described above, the correlations with SPI and SSI generally behave similarly during the winter months – i.e. the wet-dry signatures in rainfall cascade down and are identifiable in streamflow patterns. In the summer months the NAOI-SPI correlations for the majority of catchments are negative. In the NAOI-SSI correlations, the summer values, while still negative, are notably weaker. The catchments with the weakest NAOI-SSI correlations are those generally in the central/southern region. These catchments have very slow response times due to their characteristics which may moderate the NAO wet/dry rainfall deviation.</p>

Spatio-temporal patterns of pressure over the North Atlantic

2010 ◽  
Vol 30 (15) ◽  
pp. 2257-2263 ◽  
Author(s):  
Sílvia Antunes ◽  
Oliveira Pires ◽  
Alfredo Rocha
Keyword(s):  
North Atlantic ◽  
Temporal Patterns ◽  
The North ◽  
The North Atlantic ◽  
Spatio Temporal

scholarly journals Intercomparison of Data-Driven and Learning-Based Interpolations of Along-Track Nadir and Wide-Swath SWOT Altimetry Observations

2020 ◽  
Vol 12 (22) ◽  
pp. 3806 ◽  
Author(s):  
Maxime Beauchamp ◽  
Ronan Fablet ◽  
Clément Ubelmann ◽  
Maxime Ballarotta ◽  
Bertrand Chapron
Keyword(s):  
High Resolution ◽  
North Atlantic ◽  
Data Driven ◽  
Optimal Interpolation ◽  
Observation System ◽  
The North ◽  
The North Atlantic ◽  
Spatio Temporal ◽  
Along Track ◽  
Wide Swath

Over the last few years, a very active field of research has aimed at exploring new data-driven and learning-based methodologies to propose computationally efficient strategies able to benefit from the large amount of observational remote sensing and numerical simulations for the reconstruction, interpolation and prediction of high-resolution derived products of geophysical fields. In this paper, we investigate how they might help to solve for the oversmoothing of the state-of-the-art optimal interpolation (OI) techniques in the reconstruction of sea surface height (SSH) spatio-temporal fields. We focus on two small 10°×10° GULFSTREAM and 8°×10° OSMOSIS regions, part of the North Atlantic basin: the GULFSTREAM area is mainly driven by energetic mesoscale dynamics, while OSMOSIS is less energetic but with more noticeable small spatial patterns. Based on observation system simulation experiments (OSSE), we used a NATL60 high resolution deterministic ocean simulation of the North Atlantic to generate two types of pseudo-altimetric observational dataset: along-track nadir data for the current capabilities of the observation system and wide-swath SWOT data in the context of the upcoming SWOT (Surface Water Ocean Topography) mission. We briefly introduce the analog data assimilation (AnDA), an up-to-date version of the DINEOF algorithm, and a new neural networks-based end-to-end learning framework for the representation of spatio-temporal irregularly-sampled data. The main objective of this paper consists of providing a thorough intercomparison exercise with appropriate benchmarking metrics to assess whether these approaches help to improve the SSH altimetric interpolation problem and to identify which one performs best in this context. We demonstrate how the newly introduced NN method is a significant improvement with a plug-and-play implementation and its ability to catch up the small scales ranging up to 40 km, inaccessible by the conventional methods so far. A clear gain is also demonstrated when assimilating jointly wide-swath SWOT and (aggregated) along-track nadir observations.

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