Generation mechanism of quasidecadal variability of upper ocean heat content in the equatorial Pacific Ocean

AbstractIn this study, an enhanced footprint of the interdecadal Pacific oscillation (IPO) on the upper-ocean heat content (OHC) in the South China Sea (SCS) since the 1990s is revealed. The negative OHC–IPO correlation is significant (r = −0.71) during 1990–2010 [period 2 (P2)], whereas it is statistically insignificant during 1960–80 [period 1 (P1)]. Analyses show that the scope of the equatorial Pacific wind anomalies is wider during P2 compared with that during P1 due to a larger east–west SST gradient and enhanced tropical warming in the Indian Ocean. When the IPO is negative during P2, a wider scope of the wind stress anomalies associated with the IPO could lead to 1) the southward migration of the North Equatorial Current bifurcation latitude (NECBL) by affecting the wind stress curl over the key region where it is near the climatological NECBL and 2) an increase in the interbasin pressure gradient (sea surface height difference) between the western Pacific and the SCS; these two processes strengthen the Kuroshio and weaken the Luzon Strait transport (LST) or SCS throughflow into the SCS. Also, 3) the equatorial Pacific wind anomalies are wide enough to directly weaken the LST in the SCS through the “island rule.” These three pathways finally change the oceanic gyre in the SCS and increase the OHC. Our results suggest that the scope of the tropical wind stress is the crucial factor when we consider the relationship between the upper ocean thermal conditions in the SCS and the Pacific variability.

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Intraseasonal variations of Ocean Heat Content in the tropical Indian and Pacific Ocean

10.5194/egusphere-egu21-3535 ◽

2021 ◽

Author(s):

Ashneel Chandra ◽

Noel Keenlyside ◽

Lea Svendsen ◽

Awnesh Singh

Keyword(s):

Pacific Ocean ◽

Heat Budget ◽

Heat Content ◽

Equatorial Pacific ◽

Kelvin Waves ◽

Ocean Heat Content ◽

Equatorial Pacific Ocean ◽

Budget Analysis ◽

The Earth ◽

The Indian Ocean

The ocean heat content (OHC) is an important thermodynamical parameter in the Earth&#8217;s climate system as about 90% of the Earth&#8217;s Energy Imbalance (EEI) is stored in the ocean. It is therefore important to understand how this quantity varies on different timescales and how different thermodynamical and dynamical processes affect it. On intraseasonal timescales, there is a two-way interaction between the atmosphere and ocean whereby atmospheric forcing leads to ocean dynamics causing changes in OHC and OHC, in turn, possibly playing a role in affecting the intensity of the Madden-Julian Oscillation (MJO) through air-sea interactions. In this study, we focus on the variations of OHC in the equatorial Indian and Pacific Ocean on intraseasonal timescales. A heat budget analysis for the upper 100 m was performed using HYCOM Reanalysis for the period 2005 &#8211; 2015. The simple three-term heat budget comprised of a surface heat flux term (Q), an advection and adiabatic redistribution term (ADV) and finally a residual term (RES) to account for processes not resolved using the reanalysis product. When averaged over the equatorial Pacific Ocean, the heat budget analysis shows that the&#160;ADV&#160;and RES&#160;terms contributed the most to the ocean heat content tendency (OHCT). Zonal wind anomalies are observed to excite intraseasonal Kelvin waves in the equatorial Pacific Ocean. These Kelvin waves are associated with the eastward advection of intraseasonal OHC anomalies from the western Pacific warm pool to the central Pacific. This eastward propagation of intraseasonal OHC anomalies associated with Kelvin waves is seen to contribute to the warming leading to El Ni&#241;o events such as the 2009 El Ni&#241;o. In the Indian Ocean, intraseasonal OHC anomalies along the equator were seen to be in phase with the MJO as revealed by the negative intraseasonal&#160;outgoing longwave radiation (OLR) anomalies, while the off-equatorial intraseasonal OHC anomalies&#160;were seen to be out of phase with the MJO. Off-equatorial intraseasonal OHC anomalies&#160;in the Indian Ocean may be a useful parameter to investigate further as it may provide the residual heat energy for air-sea interactions for subsequent MJO events and hence improve subseasonal predictability.

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Anomalous Oceanic Conditions in the Central and Eastern North Pacific Ocean during the 2014 Hurricane Season and Relationships to Three Major Hurricanes

Journal of Marine Science and Engineering ◽

10.3390/jmse8040288 ◽

2020 ◽

Vol 8 (4) ◽

pp. 288

Author(s):

Victoria L. Ford ◽

Nan D. Walker ◽

Iam-Fei Pun

Keyword(s):

Pacific Ocean ◽

Heat Content ◽

Ocean Heat Content ◽

Sea Surface ◽

Upper Ocean ◽

Sea Surface Temperatures ◽

Central Pacific ◽

Upper Ocean Heat Content ◽

Hurricane Season ◽

Along Track

The 2014 Northeast Pacific hurricane season was highly active, with above-average intensity and frequency events, and a rare landfalling Hawaiian hurricane. We show that the anomalous northern extent of sea surface temperatures and anomalous vertical extent of upper ocean heat content above 26 °C throughout the Northeast and Central Pacific Ocean may have influenced three long-lived tropical cyclones in July and August. Using a variety of satellite-observed and -derived products, we assess genesis conditions, along-track intensity, and basin-wide anomalous upper ocean heat content during Hurricanes Genevieve, Iselle, and Julio. The anomalously northern surface position of the 26 °C isotherm beyond 30° N to the north and east of the Hawaiian Islands in 2014 created very high sea surface temperatures throughout much of the Central Pacific. Analysis of basin-wide mean conditions confirm higher-than-average storm activity during strong positive oceanic thermal anomalies. Positive anomalies of 15–50 kJ cm−2 in the along-track upper ocean heat content for these three storms were observed during the intensification phase prior to peak intensity, advocating for greater understanding of the ocean thermal profile during tropical cyclone genesis and development.

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