scholarly journals Spurious North Tropical Atlantic pre-cursors to ENSO

2021 ◽  
Author(s):  
Wenjun Zhang ◽  
Feng Jiang ◽  
Malte Stuecker ◽  
Fei-Fei Jin ◽  
Axel Timmermann
Keyword(s):  
Cross Correlation ◽  
Southern Oscillation ◽  
Global Climate ◽  
Sea Surface ◽  
Time Varying ◽  
Tropical Atlantic ◽  
The North ◽  
Sst Variability ◽  
Primary Driver ◽  
North Tropical Atlantic

Abstract The El Niño-Southern Oscillation (ENSO), the primary driver of year-to-year global climate variability, is known to influence the North Tropical Atlantic (NTA) sea surface temperature (SST), especially during boreal spring season. Focusing on statistical lead-lag relationships, previous studies have proposed that interannual NTA SST variability can also feed back on ENSO in a predictable manner. However, these studies do not properly account for ENSO’s autocorrelation and the fact that the SST in the Atlantic and Pacific, as well as their atmospheric interaction are seasonally modulated. This can lead to misinterpretations of causality and the spurious identification of Atlantic precursors for ENSO. Revisiting this issue under consideration of seasonality, time-varying ENSO frequency, and greenhouse warming, we demonstrate that the cross-correlation characteristics between NTA SST and ENSO, are fully consistent with a one-way Pacific to Atlantic forcing, even though the interpretation of lead-lag relationships may suggest otherwise.

scholarly journals Spurious North Tropical Atlantic precursors to El Niño

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Wenjun Zhang ◽  
Feng Jiang ◽  
Malte F. Stuecker ◽  
Fei-Fei Jin ◽  
Axel Timmermann
Keyword(s):  
El Niño ◽  
Cross Correlation ◽  
El Nino ◽  
Southern Oscillation ◽  
Global Climate ◽  
Tropical Atlantic ◽  
The North ◽  
Sst Variability ◽  
Primary Driver ◽  
North Tropical Atlantic

AbstractThe El Niño-Southern Oscillation (ENSO), the primary driver of year-to-year global climate variability, is known to influence the North Tropical Atlantic (NTA) sea surface temperature (SST), especially during boreal spring season. Focusing on statistical lead-lag relationships, previous studies have proposed that interannual NTA SST variability can also feed back on ENSO in a predictable manner. However, these studies did not properly account for ENSO’s autocorrelation and the fact that the SST in the Atlantic and Pacific, as well as their interaction are seasonally modulated. This can lead to misinterpretations of causality and the spurious identification of Atlantic precursors for ENSO. Revisiting this issue under consideration of seasonality, time-varying ENSO frequency, and greenhouse warming, we demonstrate that the cross-correlation characteristics between NTA SST and ENSO, are consistent with a one-way Pacific to Atlantic forcing, even though the interpretation of lead-lag relationships may suggest otherwise.

scholarly journals Greenhouse warming intensifies north tropical Atlantic climate variability

2021 ◽  
Vol 7 (35) ◽  
pp. eabg9690
Author(s):  
Yun Yang ◽  
Lixin Wu ◽  
Ying Guo ◽  
Bolan Gan ◽  
Wenju Cai ◽  
...  
Keyword(s):  
Climate Variability ◽  
Southern Oscillation ◽  
Greenhouse Warming ◽  
Tropospheric Temperature ◽  
Tropical Atlantic ◽  
Moist Convection ◽  
Socioeconomic Impacts ◽  
The North ◽  
Sst Variability ◽  
North Tropical Atlantic

Variability of North Tropical Atlantic (NTA) sea surface temperature (SST), characterized by a near-uniform warming at its positive phase, is a consequential mode of climate variability. Modulated by El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation, NTA warm anomalies tend to induce La Niña events, droughts in Northeast Brazil, increased frequency of extreme hurricanes, and phytoplankton blooms in the Guinea Dome. Future changes of NTA variability could have profound socioeconomic impacts yet remain unknown. Here, we reveal a robust intensification of NTA variability under greenhouse warming. This intensification mainly arises from strengthening of ENSO-forced Pacific-North American pattern and tropospheric temperature anomalies, as a consequence of an eastward shift of ENSO-induced equatorial Pacific convection and of increased ENSO variability, which enhances ENSO influence by reinforcing the associated wind and moist convection anomalies. The intensification of NTA SST variability suggests increased occurrences of extreme NTA events, with far-reaching ramifications.

Interannual sea surface chlorophyll-a signature in the tropical Atlantic

2021 ◽  
Author(s):  
Fanny Chenillat ◽  
Julien Jouanno ◽  
Serena Illig ◽  
Founi Mesmin Awo ◽  
Gaël Alory ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Cold Tongue ◽  
Equatorial Atlantic ◽  
Atlantic Region ◽  
The North ◽  
Sst Anomaly ◽  
Equatorial Band ◽  
North Tropical Atlantic

<div><span>Surface chlorophyll-<em>a </em>concentration (CHL-<em>a</em>) remotely observed by satellite shows a marked seasonal and interannual variability in the Tropical Atlantic, with potential consequences on the marine trophic web. Seasonal and interannual CHL-<em>a </em>variability peaks in boreal summer and shows maxima in the equatorial Atlantic region at 10˚W, spreading from 0 to 30˚W. In this study, we analyze how the remotely-sensed surface CHL-<em>a </em>responds to the leading climate modes affecting the interannual equatorial Atlantic variability over the 1998-2018 period, namely the Atlantic Zonal Mode (AZM) and the North Tropical Atlantic Mode (NTA, also known as the Atlantic Meridional Mode). The AZM is characterized by anomalous warming (or cooling) along the eastern equatorial band. In contrast, the NTA is characterized by an interhemispheric pattern of the sea surface temperature (SST), with anomalous warm (cold) conditions in the north tropical Atlantic region and weak negative (positive) SST anomalies south of the equator. We show that both modes significantly drive the interannual Tropical Atlantic surface CHL-<em>a </em>variability, with different timings and contrasted modulation on the eastern and western portions of the cold tongue area. Our results also reveal that the NTA slightly dominates (40%) the summer tropical Atlantic interannual variability over the last two decades, most probably because of a positive phase of the Atlantic multidecadal oscillation. For each mode of variability, we analyze an event characterized by an extreme negative sea surface temperature (SST) anomaly in the Atlantic equatorial band. Both modes are associated with a positive CHL-<em>a </em>anomaly at the equator. In 2002, a negative phase of the NTA led to cold SST anomaly and high positive CHL-<em>a </em>in the western portion of the cold tongue, peaking in June-July and lasting until the end of the year. In contrast, in 2005, a negative phase of the AZM drove cool temperature and positive CHL-<em>a </em>in the eastern equatorial band, with a peak in May-June and almost no signature after August. Such contrasted year to year conditions can affect the marine ecosystem by changing temporal and spatial trophic niches for pelagic predators, thus inducing significant variations for ecosystem functioning and fisheries.</span></div>

scholarly journals Is There Evidence of Changes in Tropical Atlantic Variability Modes under AMO Phases in the Observational Record?

2018 ◽  
Vol 31 (2) ◽  
pp. 515-536 ◽  
Author(s):  
Marta Martín-Rey ◽  
Irene Polo ◽  
Belén Rodríguez-Fonseca ◽  
Teresa Losada ◽  
Alban Lazar
Keyword(s):  
Southern Oscillation ◽  
Walker Circulation ◽  
Atlantic Multidecadal Oscillation ◽  
Boreal Summer ◽  
Tropical Atlantic ◽  
Equatorial Atlantic ◽  
The North ◽  
Sst Variability ◽  
Tropical Atlantic Variability ◽  
Atlantic Niño

The Atlantic multidecadal oscillation (AMO) is the leading mode of Atlantic sea surface temperature (SST) variability at multidecadal time scales. Previous studies have shown that the AMO could modulate El Niño–Southern Oscillation (ENSO) variance. However, the role played by the AMO in the tropical Atlantic variability (TAV) is still uncertain. Here, it is demonstrated that during negative AMO phases, associated with a shallower thermocline, the eastern equatorial Atlantic SST variability is enhanced by more than 150% in boreal summer. Consequently, the interannual TAV modes are modified. During negative AMO, the Atlantic Niño displays larger amplitude and a westward extension and it is preceded by a simultaneous weakening of both subtropical highs in winter and spring. In contrast, a meridional seesaw SLP pattern evolving into a zonal gradient leads the Atlantic Niño during positive AMO. The north tropical Atlantic (NTA) mode is related to a Scandinavian blocking pattern during winter and spring in negative AMO, while under positive AMO it is part of the SST tripole associated with the North Atlantic Oscillation. Interestingly, the emergence of an overlooked variability mode, here called the horseshoe (HS) pattern on account of its shape, is favored during negative AMO. This anomalous warm (cool) HS surrounding an eastern equatorial cooling (warming) is remotely forced by an ENSO phenomenon. During negative AMO, the tropical–extratropical teleconnections are enhanced and the Walker circulation is altered. This, together with the increased equatorial SST variability, could promote the ENSO impacts on TAV. The results herein give a step forward in the better understanding of TAV, which is essential to improving its modeling, impacts, and predictability.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

scholarly journals Long term trends in the sea surface temperature of the Black Sea

Ocean Science ◽  
2010 ◽  
Vol 6 (2) ◽  
pp. 491-501 ◽  
Author(s):  
G. I. Shapiro ◽  
D. L. Aleynik ◽  
L. D. Mee
Keyword(s):  
Surface Temperature ◽  
Sea Surface Temperature ◽  
Black Sea ◽  
Sea Surface ◽  
The Black Sea ◽  
The North ◽  
Sst Variability ◽  
Long Term Trends ◽  
Cooling Trend

Abstract. There is growing understanding that recent deterioration of the Black Sea ecosystem was partly due to changes in the marine physical environment. This study uses high resolution 0.25° climatology to analyze sea surface temperature variability over the 20th century in two contrasting regions of the sea. Results show that the deep Black Sea was cooling during the first three quarters of the century and was warming in the last 15–20 years; on aggregate there was a statistically significant cooling trend. The SST variability over the Western shelf was more volatile and it does not show statistically significant trends. The cooling of the deep Black Sea is at variance with the general trend in the North Atlantic and may be related to the decrease of westerly winds over the Black Sea, and a greater influence of the Siberian anticyclone. The timing of the changeover from cooling to warming coincides with the regime shift in the Black Sea ecosystem.

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