On the seasonal variations of ocean bottom pressure in the world oceans

Abstract

Seasonal variability of the ocean bottom pressure (OBP) in the world oceans is investigated using 15 years of GRACE observations and a Pressure Coordinate Ocean Model (PCOM). In boreal winter, negative OBP anomalies appear in the northern North Pacific, subtropical South Pacific and north of 40 °S in the Indian Ocean, while OBP anomaly in the Southern Ocean is positive. The summer pattern is opposite to that in winter. The centers of positive (negative) OBP signals have a good coherence with the mass convergence/divergence due to Ekman transport, indicating the importance of wind forcing. The PCOM model reproduces the observed OBP quite well. Sensitivity experiments indicate that wind forcing dominates the regional OBP seasonal variations, while the contributions due to heat flux and freshwater flux are unimportant. Experiments with daily sea level pressure (SLP) forcing suggest that at high frequencies the non-static effect of SLP is not negligible.

Seasonal modulation of oceanic seismicity in the azores

“…However, these models can only simulate consistent patterns of bottom pressure variability on monthly and longer time scales away from areas with high mesoscale eddy activity (Androsov et al, 2020). Mass conservation models indicate that wind forcing dominates regional OBP variations (Cheng et al, 2021;Niu et al, 2022), and OBP change is known to contribute to approximately 60% of the global mean sea level rise (Chambers et al, 2017). An open question that remains to be investigated is how the strong wind forcing and mesoscale eddy activity observed in the Azores is reflected into OBP variations.…”

“…Because the lags are not constant, it is still not clear if the seismicity rate is proportional to the stress rate or to the stress amplitude associated with GRACE or OBP. OBP variations at mid-high latitudes on sub-seasonal to interannual timescales are mainly affected by wind forcing (Niu et al, 2022), the hydrological cycle (Chambers et al, 2004), atmospheric pressure (Cheng et al, 2021) and baroclinic processes (Vinogradova et al, 2007). In addition to this forced variability, the OBP may have chaotic intrinsic variability in eddy-active regions, arising from non-linear ocean processes () Zhao et al, 2021.…”

“…5 °in both latitude and longitude, the JPL MASCON grid has a native resolution of only 3 °x 3 °in size. Early studies showed a good match between the GRACE estimates, large-scale OBP and global mean sea level from altimetry (Chambers et al, 2004), however subsequent studies showed that the link between sea level and OBP derived from GRACE is broken by baroclinic processes, depending on spatial and temporal scales as well as on the geographic region (Ponte et al, 2007;Bingham and Hughes, 2008;Chambers and Schroter, 2011;Zhang et al, 2018, Chen et al, 2021. Recent research also indicates that the comparison between GRACE and in-situ OBP measurements is often not satisfactory not only because of GRACE's low spatial and temporal resolution, but also due to a chaotic intrinsic variability resulting from the non-linear interactions between oceanic and atmospheric processes (Zhao et al, 2021).…”

The Global Patterns of Interannual and Intraseasonal Mass Variations in the Oceans from GRACE and GRACE Follow-On Records

“…Our study is part of this empirical process of understanding and targets the global detection of regionally consistent spatiotemporal patterns within the GRACE (-FO) data. In the literature, such global studies often consist of global sea-level budgets and comparisons with other models or datasets [14][15][16][17][18][19]. Besides, except for some studies focusing on interannual or intraseasonal variations [20,21], most of these global ocean studies focus on trends or seasonal cycles given the substantial variance that is attributed to these components alongside anthropic concerns about sea-level rise.…”

The Global Patterns of Interannual and Intraseasonal Mass Variations in the Oceans from GRACE and GRACE Follow-On Records

“…Our study is part of this empirical process of understanding and targets the global detection of regionally consistent spatiotemporal patterns within the GRACE (-FO) data. In the literature, such global studies often consist of global sea-level budgets and comparisons with other models or datasets [14][15][16][17][18][19]. Besides, except for some studies focusing on interannual or intraseasonal variations [20,21], most of these global ocean studies focus on trends or seasonal cycles given the substantial variance that is attributed to these components alongside anthropic concerns about sea-level rise.…”