On Sea Level Along the Brazilian Coast

Abstract

ABSTRACT. This is Part II of a contribution on Brazilian sea levels -Part I dealt with the seasonal variability. It examines the sea level changes along the Brazilian coast from series with less than 40 years of measurement, against the background of changes in series of all continents and islands around the world, considering data distributed by the Permanent Service for Mean Sea Level (PSMSL). The method of analysis follows the display of the data in a: 1) first plot of relative sea level trends (C), against the length of the series (L) expressed in years and a: 2) second plot showing the relative sea level regression coefficients (C), versus the corresponding correlation values (m). The first plot of all PSMSL data exhibited a cusped like shape of the distribution of (C), having maxima values about 10-20 cm/cty for the longest series (120-137 years), indicating the overall positive value of the global relative sea level trend. Similar first plot, a regional plot of African and South American data adjusted to the same global relative mean level, showed that the Brazilian trends (C), are mostly concentrated in the positive side of the cusped: (ports of Belém, Fortaleza. Recife, Canavieiras, Salvador, Ilha Fiscal, Rio de Janeiro, Ubatuba, Cananeia, and Imbituba) which have a mean value within 30 to 40 cm/cty. The second plot, with all set of PSMSL data, was necessary in order to display trend values of non simultaneous series of different continental borders and lengths in the same bin. The plot gave two different linear inclinations for trend values within ±0.3 cm/y, in the positive and negative sides of the figure. The global ratio obtained for the trends was R = −1.2, suggesting also, from the linearity of the plot, that the trends and correlation values are statistically dependent variables. The graph produced a different value for global balance of the value C obtained in the first plot. Similar regional second plot of the African Atlantic and South American borders, which include the Brazilian data, also gave rise to two new regression lines with trend C*1<0 and C*2>0, with a ratio R = −2.2, involving bins of m and C values that are also null in the vicinity of zero. This regionally plot confirmed the result of the second plot with PSMSL series that they (C and m), globally, should be dependent statistical variables. These findings, however, do not change the fact that the regional series with trends 0.2 cm/year have correlation values m<0.3, whatever their lengths, and that the mean value of the relative sea level, along the Brazilian coast, is increasing with an estimated rate of 30 to 40 cm/cty. Further work is under way, aiming at solving the above apparently contradictory results.Keywords: sea level, Brazilian coast, PSMSL series, global relative sea level, imbalance of relative sea level. RESUMO.Estaé a segunda parte de uma contribuição sobre os níveis do mar na costa brasileira -a parte I tratou da variação sazonal -ela examina as mudanças do nível do mar ao longo da costa brasileira a partir de sér...

Sea-land limits: a case study

“…1), were similar, so that the above hypotheses could be accepted and adopted for transferring these levels, as shown in Mesquita 1994Mesquita , 1998Mesquita , 2003 (See also www.mares.io.usp.br, icon "Praias Arenosas" -Sandy Beaches).…”

Hotspots of Relative Sea Level Rise in the Tropics

“…A different trend was found, however, by Ducarme et al [2007] who estimated a larger RSL trend of 5.6 ± 0.07 mm/year after having identified and corrected two periodicities of 24.2 year and 10.7 year dominating the very low frequency spectrum of sea level at Cananeia. This rate, over the last 50 years, largely exceeds the observed GMSL trend from satellite altimetry over the last 22 years (3.1 to 3.3 mm/yr, [Cazenave and Le Cozannet 2013]) and Cananeia should be classed as a strong positive anomaly, a hotspot, in the global sea level rise pattern [Mesquita et al 2013]. The reasons of the increased rate of RSL rise at Cananeia have not been completely explained yet, but they are unlikely due to land subsidence alone.…”

“…The lower trends were suggested to result from land movement produced at Recife by the Pernambuco fault, and to sediment-induced subsidence at Imbituba and Belem. More recent work has revisited these long-term trends and estimated RSL trend in the range 3-5 mm/yr over the past 50 years [Neves and Muehe 1995;Mesquita 2003;Muehe 2006;Mesquita et al 2013]. We searched for new records in PSMSL to update the Emery and Aubrey results, but have found only two recent series: One at Cananeia and another at Ihla Fiscal (Table 4.1).…”

“…[1988], Muehe and Neves [1995] and Mesquita et al [2013] previously presented evidence that the Brazilian coast may be sinking.) An apparent contradiction comes from the NEIA GPS station collocated (Table 4.1) with the Cananeia TG (10 m distance from the tide-gauge and 15 years in operation).…”

Vulnerabilidade costeira e perda de ambientes devido à elevação do nível do mar no litoral sul do Rio Grande do Sul

“…No que se refere à média das mudanças do nível médio do mar feitas no Brasil, os dados sobre o comportamento atual do nível médio do mar possuem disponibilidade limitada, o que, eleva a incerteza para os modelos de resposta costeira para o futuro aumento do nível do mar. No Brasil, poucos locais apresentam registros suficientes para permitir comparações climáticas (Mesquita, 2003). Apenas no ano de 2004 houve a implantação do Sistema Global de Observação do Nível do Mar (GLOSS), coordenado pelo Centro de Hidrografia da Marinha do Brasil (CHM).…”