scholarly journals Low-Frequency Sea Level Variability and the Inverted Barometer Effect

2006 ◽  
Vol 23 (4) ◽  
pp. 619-629 ◽  
Author(s):  
Rui M. Ponte
Keyword(s):  
Sea Level ◽  
Tide Gauge ◽  
Low Frequency ◽  
Anomalous Behavior ◽  
Global Ocean ◽  
Sea Level Pressure ◽  
Seasonal Signals ◽  
Global Mean Sea Level ◽  
Inverted Barometer ◽  
Linear Trends

Abstract For a dynamical interpretation of sea level records, estimates are needed of the isostatic, or so-called inverted barometer, signals (ηib) associated with the ocean response to atmospheric loading. Seasonal and longer-period ηib signals are evaluated over the global ocean for the period 1958–2000 using monthly sea level pressure fields from two different atmospheric reanalyses. Variability and linear trends in ηib agree well for the two reanalyses in most regions but less so over the Southern Ocean, where uncertainties in ηib seem to be largest. The standard deviation of ηib ranges from <1 cm in equatorial regions to >7 cm in the regions of the Aleutian and Iceland lows and parts of the Southern and Arctic Oceans. When compared to a global tide gauge dataset, both seasonal and interannual ηib signals are found to contribute importantly to the sea level variance in many mid- and high-latitude records, with seasonal signals important as well in tropical records from India and Southeast Asia. For these records, subtracting ηib from the data can lead to changes in variance of 40% or more. Over the period of study, linear trends in ηib are mostly negative at low and midlatitudes and can cause negative biases in tide gauge estimates of global mean sea level rise that are comparable in magnitude to the effects of postglacial rebound. In agreement with previous findings, ηib signals are found to introduce anomalous behavior in local records (e.g., substantially weaker upward trends in the Mediterranean), and their removal can also reduce formal trend uncertainties. Accounting for ηib effects can be even more important when analyzing relatively short (decadal) records, such as those available from satellite altimetry.

scholarly journals Interannual to decadal variability within and across the major Eastern Boundary Upwelling Systems

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Giulia Bonino ◽  
Emanuele Di Lorenzo ◽  
Simona Masina ◽  
Doroteaciro Iovino
Keyword(s):  
Climate Change ◽  
Climate Variability ◽  
Sea Level ◽  
Low Frequency ◽  
Global Ocean ◽  
Thermocline Depth ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Eastern Boundary ◽  
Low Frequency Variability

AbstractClimate variability and climate change in Eastern Boundary Upwelling Systems (EBUS) affect global marine ecosystems services. We use passive tracers in a global ocean model hindcast at eddy-permitting resolution to diagnose EBUS low-frequency variability over 1958–2015 period. The results highlight the uniqueness of each EBUS in terms of drivers and climate variability. The wind forcing and the thermocline depth, which are potentially competitive or complementary upwelling drivers under climate change, control EBUS low-frequency variability with different contributions. Moreover, Atlantic and Pacific upwelling systems are independent. In the Pacific, the only coherent variability between California and Humboldt Systems is associated with El Niño Southern Oscillation. The remaining low-frequency variance is partially explained by the North and South Pacific expressions of the Meridional Modes. In the Atlantic, coherent variability between Canary and Benguela Systems is associated with upwelling trends, which are not dynamically linked and represent different processes. In the Canary, a negative upwelling trend is connected to the Atlantic Multi-decadal Oscillation, while in the Benguela, a positive upwelling trend is forced by a global sea level pressure trend, which is consistent with the climate response to anthropogenic forcing. The residual variability is forced by localized offshore high sea level pressure variability.

scholarly journals New Insights into Annual and Semiannual Cycles of Sea Level Pressure

2012 ◽  
Vol 140 (4) ◽  
pp. 1347-1355 ◽  
Author(s):  
Ge Chen ◽  
Chengcheng Qian ◽  
Caiyun Zhang
Keyword(s):  
Sea Level ◽  
Southern Oscillation ◽  
Global Ocean ◽  
Boreal Winter ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The North ◽  
Dominant Feature ◽  
The One ◽  
The North Pacific

Sea level pressure (SLP) acts, on the one hand, as a “bridge parameter” to which geophysical properties at the air–sea interface (e.g., wind stress and sea surface height) are linked, and on the other hand, as an “index parameter” by which major atmospheric oscillations, including the well-known Southern Oscillation, are defined. Using 144 yr (1854–1997) of extended reconstructed SLP data, seasonal patterns of its variability are reinvestigated in detail. New features on fundamental structure of its annual and semiannual cycles are revealed in two aspects. First, the spatiotemporal patterns of yearly and half-yearly SLPs are basically determined by a network of “amphidromes,” which are surrounded by rotational variations. Fourteen cyclonic and anticyclonic annual SLP amphidromes (half each and often in pair) are found in the global ocean, while the numbers of the two types of semiannual amphidrome are 11 and 9, respectively. The second dominant feature in SLP variability is the pattern of oscillation or seesaw for both annual and semiannual components. At least eight oscillation zones are identified for the annual cycle, which can be categorized into a boreal winter mode and an austral winter mode. As for the semiannual cycle, the seesaw pattern is geographically divided into three regimes: the North Pacific regime, the North Atlantic regime, and the Southern Ocean regime. These findings serve as a new contribution to characterizing and understanding the seasonality of the global ocean–atmosphere system.

How Salty Is the Global Ocean: Weighting It All or Tasting It a Sip at a Time?

2020 ◽  
Author(s):  
Rui Ponte ◽  
Qiang Sun ◽  
Chao Liu ◽  
Xinfeng Liang
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Hydrological Cycle ◽  
Global Ocean ◽  
Data Quality Control ◽  
Argo Data ◽  
Terrestrial Water ◽  
Control Procedures ◽  
Global Mean Sea Level

<div class="page" title="Page 1"> <div class="section"> <div class="layoutArea"> <div class="column"> <p>Global ocean mean salinity <em>S </em>is a key indicator of the Earth's hydrological cycle and the exchanges of freshwater between the terrestrial water and ice reservoirs and the ocean. We explore two different ways of determining how salty the ocean is: (1) use in situ salinity measurements to taste the ocean a sip at a time and obtain a sample average; (2) use space gravimetry to weigh the whole ocean including sea-ice, and then separate sea-ice effects to infer changes in liquid freshwater content and thus <em>S</em>. Focusing on the 2005-2019 period, we assess monthly series of <em>S </em>derived from five different in situ gridded products, based mostly but not exclusively on Argo data, versus a series obtained from GRACE and GRACE Follow-On data and available sea ice mass estimates.</p> <p>There is little consistency in <em>S </em>series from the two methods for all time scales examined (seasonal, interannual, long-term trend). In situ series show larger variability, particularly at the longest scales, and are somewhat incoherent with the GRACE-derived series. In addition, there are wide spread differences among all the in situ <em>S </em>series, which denote their considerable sensitivity to choice of data, quality control procedures, and mapping methods. Results also suggest that in situ <em>S </em>values are prone to systematic biases, with most series showing increases after around 2014 that are equivalent to a drop in barystatic sea level of tens of centimeters! Estimates derived from GRACE are much smaller in magnitude and consistent with contributions of freshwater to the global mean sea level budgets, and they are thus more reliable than in situ-based <em>S </em>estimates. The existence of GRACE-derived estimates can serve as a consistency check on in situ measurements, revealing potential unknown biases and providing a way to cross-calibrate the latter data.</p> </div> </div> </div> </div>

scholarly journals GEOCENTRIC MEAN SEA LEVEL FIELDS AT THE GERMAN NORTH SEA AND BALTIC COAST

2018 ◽  
pp. 21
Author(s):  
Jessica Kelln ◽  
Sönke Dangendorf ◽  
Jürgen Jensen ◽  
Justus Patzke ◽  
Wolfgang Niemeier ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Tide Gauge ◽  
Last Deglaciation ◽  
Mean Sea Level ◽  
Baltic Coast ◽  
Vertical Land Motion ◽  
Level Information ◽  
The Last Deglaciation ◽  
Global Mean Sea Level

Global mean sea level has risen over the 20th century (Hay et al. 2015; Dangendorf et al. 2017) and under sustained greenhouse gas emissions it is projected to further accelerate throughout the 21st century (Church et al. 2013) with large spatial variations, significantly threatening coastal communities. Locally the effects of geocentric (sometimes also referred to absolute) sea level rise can further be amplified by vertical land motion (VLM) due to natural adjustments of the solid earth to the melting of the large ice-sheets during the last deglaciation (GIA) or local anthropogenic interventions such as groundwater or gas withdrawal (e.g. Santamaría-Gómez et al. 2017). Both, the observed and projected geocentric sea level rise as well as VLM are critically important for coastal planning and engineering, since only their combined effect determines the total threat of coastal flooding at specific locations. Furthermore, due large spatial variability of sea level, information is required not only at isolated tide gauge (TG) locations but also along the coastline stretches in between.

scholarly journals Relationship between the Persian Gulf Sea-Level Fluctuations and Meteorological Forcing

2020 ◽  
Vol 8 (4) ◽  
pp. 285
Author(s):  
Naghmeh Afshar-Kaveh ◽  
Mostafa Nazarali ◽  
Charitha Pattiaratchi
Keyword(s):  
Sea Level ◽  
Persian Gulf ◽  
Atmospheric Pressure ◽  
Tide Gauge ◽  
Low Frequency ◽  
Northern Coast ◽  
Meteorological Forcing ◽  
Sea Level Fluctuations ◽  
Coastal Sea ◽  
The Persian Gulf

Sea-level data from six tide gauge stations along the northern coast of the Persian Gulf were analyzed both in time and frequency domain to evaluate meteorological forcing. Spectral analyses indicated that mixed, predominantly semi-diurnal tides were dominant at all stations, but low-frequency fluctuations correlated well with atmospheric pressure and wind components. Non-tidal sea-level fluctuations up to 0.75 m were observed along the northern coasts of the Gulf due to the combined action of lower atmospheric pressure and cross-shore wind. Coherency between low-frequency sea-level records and mean sea-level pressure indicated that the latter usually leads to sea-level fluctuations between 1 and 6.4 days. In contrast, the same analysis on the wind velocity and sea level revealed that the former lags between 3 and 13 days. The effect of wind stress on coastal sea-level variations was higher compared with the effect of atmospheric pressure. Concurrent analysis of low-pass-filtered sea-level records proved that the non-tidal wave moves from west to east along the northern coasts of the Persian Gulf.

scholarly journals Global ocean freshening, ocean mass increase and global mean sea level rise over 2005–2015

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
William Llovel ◽  
S. Purkey ◽  
B. Meyssignac ◽  
A. Blazquez ◽  
N. Kolodziejczyk ◽  
...  
Keyword(s):  
Sea Level ◽  
Global Ocean ◽  
Last Deglaciation ◽  
Mean Sea Level ◽  
Isostatic Adjustment ◽  
Ocean Mass ◽  
Grace Data ◽  
Global Mean Sea Level ◽  
Gravity Recovery ◽  
Global Mean

AbstractGlobal mean sea level has experienced an unabated rise over the 20th century. This observed rise is due to both ocean warming and increasing continental freshwater discharge. We estimate the net ocean mass contribution to sea level by assessing the global ocean salt budget based on the unprecedented amount of in situ data over 2005–2015. We obtain the ocean mass trends of 1.30 ± 1.13 mm · yr−1 (0–2000 m) and 1.55 ± 1.20 mm · yr−1 (full depth). These new ocean mass trends are smaller by 0.63–0.88 mm · yr−1 compared to the ocean mass trend estimated through the sea level budget approach. Our result provides an independent validation of Gravity Recovery And Climate Experiment (GRACE)-based ocean mass trend and, in addition, places an independent constraint on the combined Glacial Isostatic Adjustment – the Earth’s delayed viscoelastic response to the redistribution of mass that accompanied the last deglaciation- and geocenter variations needed to directly infer the ocean mass trend based on GRACE data.

LEVEL VARIABILITY OF THE SEA OF OKHOTSK COASTAL AREAS AT THE BEGINING OF THE 21ST CENTURY AND ITS REPRESENTATIONIN THE GLOBAL REANALYSIS DATABASES

2020 ◽  
Vol 42 (4) ◽  
pp. 411-424
Author(s):  
Aleksandr KHOLOPTSEV ◽  
Sergey PODPORIN
Keyword(s):  
Sea Level ◽  
Sea Of Okhotsk ◽  
Tide Gauge ◽  
Coastal Areas ◽  
Global Ocean ◽  
Satellite Monitoring ◽  
Climate Data ◽  
Sea Levels ◽  
The Sea Of Okhotsk

The paper aims to investigate basic features of modern long-term variations of the Okhotsk Sea level in its coastal areas and establish feasibility of certain retrospective analysis databases usage for determination of mean rates of the above processes. The reanalysis databases considered include Global Ocean Physics Reanalysis GLORYS12v.1 by the Copernicus Marine Environment Monitoring Service and ICDC-reanalysis supported by the Integrated Climate Data Center, which provide coverage of the sea in question. The raised problem is of significant interest for physiographers, oceanographers and involved in coastal shipping and marine safety in the Sea of Okhotsk. Long-term sea level variations are most accurately monitored by tide gauge stations, which, however, are scarce along the coast of the sea in question. Less accurate and not uniformly available through easier to use and collect data is the satellite monitoring by radar altimeters. Global retrospective analyses based on mathematical modelling are considered to be an effective instrument to assess sea levels at any given time at any point.

scholarly journals Sea level accelerations at globally distributed tide gauge stations during the satellite altimetry era

2018 ◽  
Vol 8 (1) ◽  
pp. 130-135 ◽  
Author(s):  
H. Bâki Iz ◽  
C. K. Shum ◽  
C. Y. Kuo
Keyword(s):  
Sea Level ◽  
Satellite Altimetry ◽  
Tide Gauge ◽  
Tide Gauge Data ◽  
Trend Model ◽  
Gauge Data ◽  
Sea Level Variations ◽  
Global Mean Sea Level ◽  
Globally Distributed ◽  
Global Mean

Abstract This observational study reports that several globally distributed tide gauge stations exhibit a propensity of statistically significant sea level accelerations during the satellite altimetry era. However, the magnitudes of the estimated tide gauge accelerations during this period are systematically and noticeably smaller than the global mean sea level acceleration reported by recent analyses of satellite altimetry. The differences are likely to be caused by the interannual, decadal and interdecadal sea level variations, which are modeled using a broken trend model with overlapping harmonics in the analyses of tide gauge data but omitted in the analysis of satellite altimetry.

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