Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE

Mazloff, Matthew R.; Böening, Carmen

doi:10.1002/2016gl068474

Cited by 17 publications

(17 citation statements)

References 29 publications

(33 reference statements)

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“…The uncertainties for each observing system (Table ) are based on comparisons with tide gauges (for SSH), ocean models and bottom pressure recorders (for SSH Mass ) [ Chambers and Bonin , ; Mazloff and Boening , ], and on temperature and salinity errors at each grid point contained in JAMSTEC data (for SSL 2000 ). The linear trend uncertainties are the 95% confidence intervals accounting for the slope in the data and random measurement errors (fourth column of Table ).…”

Section: Methodsmentioning

confidence: 99%

Decade‐long deep‐ocean warming detected in the subtropical South Pacific

Volkov

Lee

Landerer

et al. 2017

Geophysical Research Letters

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The persistent energy imbalance at the top of the atmosphere, inferred from satellite measurements, indicates that the Earth's climate system continues to accumulate excess heat. As only sparse and irregular measurements of ocean heat below 2000 m depth exist, one of the most challenging questions in global climate change studies is whether the excess heat has already penetrated into the deep ocean. Here we perform a comprehensive analysis of satellite and in situ measurements to report that a significant deep‐ocean warming occurred in the subtropical South Pacific Ocean over the past decade (2005–2014). The local accumulation of heat accounted for up to a quarter of the global ocean heat increase, with directly and indirectly inferred deep ocean (below 2000 m) contribution of 2.4 ± 1.4 and 6.1–10.1 ± 4.4%, respectively. We further demonstrate that this heat accumulation is consistent with a decade‐long intensification of the subtropical convergence, possibly linked to the persistent La Niña‐like state.

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Section: Methodsmentioning

confidence: 99%

Decade‐long deep‐ocean warming detected in the subtropical South Pacific

Volkov

Lee

Landerer

et al. 2017

Geophysical Research Letters

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“…The change in Earth orientation driven by shift in the inertia tensor causes both solid Earth deformation and sea-level change (Lambeck, 1980). The net effects of the change in orientation of Earth's spin axis thus provide a rotational feedback (e.g., Milne and Mitrovica, 1998). We may compute r and U r based on the perturbation in Earth's inertia tensor due to the global surface mass redistribution described by L (Eq.…”

Section: The Sea-level Equationmentioning

confidence: 99%

“…We may express changes in rotational potential in terms of changes in Earth's rotation parameters, moment of inertia, and hence surface loading function. Considering leading-order terms only, we get the following nonzero coefficients (Milne and Mitrovica, 1998):…”

Section: Appendix A: Theory Of the Sea-level Fingerprintmentioning

confidence: 99%

Sea-level fingerprints emergent from GRACE mission data

Adhikari

Ivins

Frederikse

et al. 2019

Earth Syst. Sci. Data

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Abstract. The Gravity Recovery and Climate Experiment (GRACE) mission data have an important, if not revolutionary, impact on how scientists quantify the water transport on the Earth's surface. The transport phenomena include land hydrology, physical oceanography, atmospheric moisture flux, and global cryospheric mass balance. The mass transport observed by the satellite system also includes solid Earth motions caused by, for example, great subduction zone earthquakes and glacial isostatic adjustment (GIA) processes. When coupled with altimetry, these space gravimetry data provide a powerful framework for studying climate-related changes on decadal timescales, such as ice mass loss and sea-level rise. As the changes in the latter are significant over the past two decades, there is a concomitant self-attraction and loading phenomenon generating ancillary changes in gravity, sea surface, and solid Earth deformation. These generate a finite signal in GRACE and ocean altimetry, and it may often be desirable to isolate and remove them for the purpose of understanding, for example, ocean circulation changes and post-seismic viscoelastic mantle flow, or GIA, occurring beneath the seafloor. Here we perform a systematic calculation of sea-level fingerprints of on-land water mass changes using monthly Release-06 GRACE Level-2 Stokes coefficients for the span April 2002 to August 2016, which result in a set of solutions for the time-varying geoid, sea-surface height, and vertical bedrock motion. We provide both spherical harmonic coefficients and spatial maps of these global field variables and uncertainties therein (https://doi.org/10.7910/DVN/8UC8IR; Adhikari et al., 2019). Solutions are provided for three official GRACE data processing centers, namely the University of Texas Austin's Center for Space Research (CSR), GeoForschungsZentrum Potsdam (GFZ), and Jet Propulsion Laboratory (JPL), with and without rotational feedback included and in both the center-of-mass and center-of-figure reference frames. These data may be applied for either study of the fields themselves or as fundamental filter components for the analysis of ocean-circulation- and earthquake-related fields or for improving ocean tide models.

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“…Changes in the Earth's gravity field accelerate or decelerate each of the satellites as they pass above them, and the resulting change in the distance between the satellites is used to infer gravity anomalies. Gravity changes over the ocean provide information on ocean mass variability, which is used for studies of the global sea level budget (Chambers et al, 2017; Leuliette & Miller, 2009) and deep ocean circulation (Landerer et al, 2015; Mazloff & Boening, 2016). Early GRACE products suffered from spurious “leakage” of the much larger terrestrial signal into the ocean, particularly near the coasts (Guo et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Decadal Strengthening of Interior Flow of North Atlantic Deep Water Observed by GRACE Satellites

2020

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The Gravity Recovery and Climate Experiment (GRACE) satellite mission provides information on changes to the Earth's gravity field, including ocean mass. Long-term trends in GRACE data are often considered unreliable due to uncertainties in the corrections made to calculate ocean mass from the raw measurements. Here, we use an independent estimate of ocean mass from satellite altimetry and in situ density data from five mooring sites and repeat hydrography to validate trends in GRACE over the North Atlantic, finding substantial agreement between the methods. The root-mean-square difference between ocean mass changes calculated with this method from the mooring data and those measured by GRACE is 3.5 mm per decade, much lower than the mean signal of 15.6 ± 1.8 mm per decade for GRACE and 17.8 ± 5.2 mm per decade for the altimetry-mooring estimate. The GRACE ocean mass data are then used to study the change in the deep circulation of the North Atlantic between the 1 April 2002 to 31 March 2009 and 1 April 2010 to 31 March 2017 periods, revealing a large-scale anticyclonic circulation anomaly off the North American coast. The change is associated with an increase of 13.9 ± 3.3 Sv (1 Sv = 10 6 m 3 s −1) of southward North Atlantic Deep Water flow in the interior between 30 • N and 40 • N, largely balanced by a northward anomaly of 10.7 ± 3.3 Sv for the boundary circulation. This implies an increased importance of interior pathways compared to the Deep Western Boundary Current for the spreading of North Atlantic Deep Water, which constitutes the lower limb of the Atlantic Meridional Overturning Circulation. Plain Language Summary The Gravity Recovery and Climate Experiment (GRACE) satellites measure the Earth's gravity field, which can be used to study ocean currents. In this study, we validate long-term trends in the data using independent ocean measurements to confirm that they reflect real changes in the ocean. In the Atlantic Ocean, North Atlantic Deep Water flows southward from its formation region near Greenland, spreading throughout the ocean basin. The flow of North Atlantic Deep Water is a crucial part of Earth's climate system, making it an important process to understand. Most of the water spreads southward in the so-called Deep Western Boundary Current along the continental shelves of North America, but there is also a significant flow further offshore in the interior of the basin. We use the GRACE data to measure changes to these two pathways between the 2002-2009 and 2010-2017 periods. The results show that southward flow in the interior has strengthened during this time, with opposite changes near the continent. This marks a significant change to how this water spreads from the formation region.

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Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE

Cited by 17 publications

References 29 publications

Decade‐long deep‐ocean warming detected in the subtropical South Pacific

Decade‐long deep‐ocean warming detected in the subtropical South Pacific

Sea-level fingerprints emergent from GRACE mission data

Decadal Strengthening of Interior Flow of North Atlantic Deep Water Observed by GRACE Satellites

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