Sea surface height changes in the North Atlantic Ocean related to the North Atlantic Oscillation

Abstract. Natural climate variability impacts the multi-decadal uptake of anthropogenic carbon dioxide (Cant) into the North Atlantic Ocean subpolar and subtropical gyres. Previous studies have shown that there is significant uptake of CO2 into the subtropical mode water (STMW) that forms south of the Gulf Stream in winter and constitutes the dominant upper-ocean water mass in the subtropical gyre of the North Atlantic Ocean. Observations at the Bermuda Atlantic Time-series Study (BATS) site near Bermuda show an increase in dissolved inorganic carbon (DIC) of +1.51 ± 0.08 μmol kg−1 yr−1 between 1988 and 2011. It is estimated that the sink of CO2 into STMW was 0.985 ± 0.018 Pg C (Pg = 1015 g C) between 1988 and 2011 (~70 % of which is due to uptake of Cant). However, the STMW sink of CO2 was strongly coupled to the North Atlantic Oscillation (NAO) with large uptake of CO2 into STMW during the 1990s (NAO positive phase). In contrast, uptake of CO2 into STMW was much reduced in the 2000s during the NAO neutral/negative phase. Thus, NAO induced variability of the STMW CO2 sink is important when evaluating multi-decadal changes in North Atlantic Ocean CO2 sinks.

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Assimilation of sea-surface temperature and altimetric observations during 1992–1993 into an eddy permitting primitive equation model of the North Atlantic Ocean

Journal of Marine Systems ◽

10.1016/s0924-7963(03)00022-8 ◽

2003 ◽

Vol 40-41 ◽

pp. 291-316 ◽

Cited By ~ 54

Author(s):

Charles-Emmanuel Testut ◽

Pierre Brasseur ◽

Jean-Michel Brankart ◽

Jacques Verron

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

North Atlantic Ocean ◽

Equation Model ◽

Sea Surface ◽

Primitive Equation ◽

The North ◽

The North Atlantic

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Chapter 28 A Model for the Sea-Surface temperature and heat Content in the North Atlantic Ocean

Coupled Ocean-Atmosphere Models - Elsevier Oceanography Series ◽

10.1016/s0422-9894(08)70724-4 ◽

1985 ◽

pp. 439-445 ◽

Cited By ~ 6

Author(s):

H. Le Treut ◽

J.Y. Simonot ◽

M. Crépon

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

North Atlantic Ocean ◽

Heat Content ◽

Sea Surface ◽

The North ◽

The North Atlantic

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Dynamical Response of the Oceanic Eddy Field to the North Atlantic Oscillation: A Model–Data Comparison

Journal of Physical Oceanography ◽

10.1175/jpo2618.1 ◽

2004 ◽

Vol 34 (12) ◽

pp. 2615-2629 ◽

Cited By ~ 45

Author(s):

Thierry Penduff ◽

Bernard Barnier ◽

W. K. Dewar ◽

James J. O'Brien

Keyword(s):

Atlantic Ocean ◽

North Atlantic Oscillation ◽

Time Scales ◽

North Atlantic ◽

Distribution Model ◽

Altimeter Data ◽

Dynamical Response ◽

The North ◽

The North Atlantic ◽

The North Atlantic Oscillation

Abstract Observational studies have shown that in many regions of the World Ocean the eddy kinetic energy (EKE) significantly varies on interannual time scales. Comparing altimeter-derived EKE maps for 1993 and 1996, Stammer and Wunsch have mentioned a significant meridional redistribution of EKE in the North Atlantic Ocean and suggested the possible influence of the North Atlantic Oscillation (NAO) cycle. This hypothesis is examined using 7 yr of Ocean Topography Experiment (TOPEX)/Poseidon altimeter data and three ⅙°-resolution Atlantic Ocean model simulations performed over the period 1979–2000 during the French “CLIPPER” experiment. The subpolar–subtropical meridional contrast of EKE in the real ocean appears to vary on interannual time scales, and the model reproduces it realistically. The NAO cycle forces the meridional contrast of energy input by the wind. The analysis in this paper suggests that after 1993 the large amplitude of the NAO cycle induces changes in the transport of the baroclinically unstable large-scale circulation (Gulf Stream/North Atlantic Current) and, thus, changes in the EKE distribution. Model results suggest that NAO-like fluctuations were not followed by EKE redistributions before 1994, probably because NAO oscillations were weaker. Strong NAO events after 1994 were followed by gyre-scale EKE fluctuations with a 4–12-month lag, suggesting that complex, nonlinear adjustment processes are involved in this oceanic adjustment.

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Analysing and projecting spatial drought conditions of the Seine catchment based on ocean-atmosphere oscillations over interannual and decadal scales

10.5194/egusphere-egu2020-4385 ◽

2020 ◽

Author(s):

Kwok Pan Chun ◽

Qing He ◽

Bastien Dieppois ◽

Nicolas Massei ◽

Matthieu Fournier

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

North Atlantic Ocean ◽

Sea Surface ◽

Positive Phase ◽

The North ◽

Drought Conditions ◽

The North Atlantic

<p>Midlatitude droughts are affected by the tropical disturbances, which are linked to sea-surface temperature patterns in the Pacific and Atlantic Oceans. The combined effects of these two ocean basins manifest themselves in the variation of streamflows, from land surface filtering. In this study, we have developed a framework to explore the effects of global sea surface temperature variations along with atmospheric teleconnection patterns, on local hydroclimatic conditions related to droughts over the Seine catchment, a main waterway in northern France. Using the Standardized Runoff-discharge Index (SRI) to quantify hydrological drought conditions over the Seine, the North Atlantic Oscillation (NAO) index was found to be a significant driver for the upstream dryness between 2001 and 2015. The El Nino Southern Oscillation (ENSO) index was also found to be a significant forcing variable, but for the Seine downstream. The Atlantic Multidecadal Oscillation (AMO) and the West Mediterranean Sea (WMED) indices were significant over almost the whole Seine River basin. Results show that the drought spatial patterns of the Seine River vary differently with the atmospheric and oceanic oscillations from interannual to decadal scales. Over a small catchment with a drainage area around 78,700 square kilometres, the spatial drought variations in the Seine catchment appear to be usual, and they are likely to be related to regional conditions which drive local land surface mechanisms linked with microclimates or geological processes. In general, during the negative phase of AMO and the positive phase of ENSO, the sea surface temperature of the North Atlantic Ocean is low. The positive phase of NAO also lowers sea surface temperatures of the North Atlantic Ocean and the West Mediterranean Sea. Droughts are likely to occur at the Seine during the negative phase of AMO and the positive phase of NAO, because the cold North Atlantic Ocean has less evaporation and provides less moisture to France. Based on these results, a statistical downscaling model is developed to relate SRI to atmospheric and oceanic oscillation indices, which are derived from the Institut Pierre Simon Laplace climate model (IPSL-CM5) outputs. Using this statistical downscaling model and scenarios of Representative Concentration Pathways (RCP4.5 and RCP8.5), the drought conditions of the Seine are projected for the mid- and long-term future (2050s and 2080s). Diverse drought results are obtained. Based on relative importance of oscillation indices, the implications of diverse projections for general drought managements in midlatitude regions related to tropical sea surface temperature disturbances and atmospheric teleconnections are discussed.</p>

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Predictability and Decadal Variability of the North Atlantic Ocean State Evaluated from a Realistic Ocean Model

Journal of Climate ◽

10.1175/jcli-d-16-0323.1 ◽

2017 ◽

Vol 30 (2) ◽

pp. 477-498 ◽

Cited By ~ 6

Author(s):

Florian Sévellec ◽

Alexey V. Fedorov

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Sea Surface Temperature ◽

North Atlantic ◽

Decadal Variability ◽

North Atlantic Ocean ◽

Meridional Overturning Circulation ◽

Sea Surface ◽

The North ◽

The North Atlantic

This study investigates the excitation of decadal variability and predictability of the ocean climate state in the North Atlantic. Specifically, initial linear optimal perturbations (LOPs) in temperature and salinity that vary with depth, longitude, and latitude are computed, and the maximum impact on the ocean of these perturbations is evaluated in a realistic ocean general circulation model. The computations of the LOPs involve a maximization procedure based on Lagrange multipliers in a nonautonomous context. To assess the impact of these perturbations four different measures of the North Atlantic Ocean state are used: meridional volume and heat transports (MVT and MHT) and spatially averaged sea surface temperature (SST) and ocean heat content (OHC). It is shown that these metrics are dramatically different with regard to predictability. Whereas OHC and SST can be efficiently modified only by basin-scale anomalies, MVT and MHT are also strongly affected by smaller-scale perturbations. This suggests that instantaneous or even annual-mean values of MVT and MHT are less predictable than SST and OHC. Only when averaged over several decades do the former two metrics have predictability comparable to the latter two, which highlights the need for long-term observations of the Atlantic meridional overturning circulation in order to accumulate climatically relevant data. This study also suggests that initial errors in ocean temperature of a few millikelvins, encompassing both the upper and deep ocean, can lead to ~0.1-K errors in the predictions of North Atlantic sea surface temperature on interannual time scales. This transient error growth peaks for SST and OHC after about 6 and 10 years, respectively, implying a potential predictability barrier.

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Disentangling the effect of ocean temperatures and isotopic content on the oxygen – isotope signals in the North Atlantic Ocean during Heinrich Event 1 using a global climate model

10.5194/cp-2016-31 ◽

2016 ◽

Author(s):

Marianne Bügelmayer-Blaschek ◽

Didier M. Roche ◽

Hans Renssen ◽

Claire Waelbroeck

Keyword(s):

Atlantic Ocean ◽

Surface Temperature ◽

Isotopic Composition ◽

Sea Surface Temperature ◽

North Atlantic ◽

North Atlantic Ocean ◽

Sea Surface ◽

The North ◽

Heinrich Event ◽

The North Atlantic

Abstract. Heinrich events are intriguing episodes of enhanced iceberg discharge occurring during the last glacial period and are characterized by a steep increase in ice rafted debris (IRD) found in North Atlantic cores. Yet, their signal is not directly recognizable in the carbonate oxygen isotopic composition recorded in planktonic foraminifera, which depends on both the prevailing temperature and isotopic composition of seawater. Using the global isotope-enabled climate – iceberg model iLOVECLIM we performed three experiments to shed light on first, the impact of the duration of a Heinrich event-like iceberg forcing on the North Atlantic Ocean and second, the mechanisms behind the simulated δ18Ocalcite pattern. We applied an iceberg forcing of 0.2 Sv for 300, 600 and 900 years, respectively, and find a strong and non-linear response of the Atlantic Meridional Overturning Circulation (AMOC) to the duration of the Heinrich event in iLOVECLIM. Moreover, our results show that the timing of the first response to the iceberg forcing coincides between all the experiments in the various regions and happens within 300 years. Furthermore, the experiments display two main patterns in the δ18Ocalcite signal. On the one hand, the central and northeast North Atlantic regions display almost no response in δ18Ocalcite to the applied iceberg forcing since the changes in sea surface temperature and δ18Oseawater compensate each other or, if the forcing is applied long enough, a delayed response is seen. On the other hand, we show that in Baffin Bay, the Nordic Seas and the subtropical North Atlantic the change in δ18Oseawater exceeds the sea surface temperature signal and there the δ18Ocalcite pattern closely follows the δ18Oseawater signal and displays a continuous decrease over the length of the Heinrich event with the minimum value at the end of the iceberg release. The comparison of the model experiments with four marine sediment cores indicates that the experiment with an iceberg forcing of 0.2 Sv for 300 years yields the most reasonable results.

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