[1] Recent studies indicate that the rates of sea level rise (SLR) along the U.S. mid-Atlantic coast have accelerated in recent decades, possibly due to a slowdown of the Atlantic Meridional Overturning Circulation (AMOC) and its upper branch, the Gulf Stream (GS). We analyzed the GS elevation gradient obtained from altimeter data, the Florida Current transport obtained from cable measurements, the North Atlantic Oscillation (NAO) index, and coastal sea level obtained from 10 tide gauge stations in the Chesapeake Bay and the mid-Atlantic coast. An Empirical Mode Decomposition/Hilbert-Huang Transformation (EMD/HHT) method was used to separate long-term trends from oscillating modes. The coastal sea level variations were found to be strongly influenced by variations in the GS on timescales ranging from a few months to decades. It appears that the GS has shifted from a 6-8 year oscillation cycle to a continuous weakening trend since about 2004 and that this trend may be responsible for recent acceleration in local SLR. The correlation between long-term changes in the coastal sea level and changes in the GS strength was extremely high (R = À0.85 with more than 99.99% confidence that the correlation is not zero). The impact of the GS on SLR rates over the past decade seems to be larger in the southern portion of the mid-Atlantic Bight near Cape Hatteras and is reduced northward along the coast. The study suggests that regional coastal sea level rise projections due to climate change must take into account the impact of spatial changes in ocean dynamics.

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[1] Sea level data from the Chesapeake Bay are used to test a novel new analysis method for studies of sea level rise (SLR). The method, based on Empirical Mode Decomposition and Hilbert-Huang Transformation, separates the sea level trend from other oscillating modes and reveals how the mean sea level changes over time. Bootstrap calculations test the robustness of the method and provide confidence levels. The analysis shows that rates of SLR have increased from $1-3 mm y À1 in the 1930s to $4-10 mm y À1 in 2011, an acceleration of $0.05-0.10 mm y À2 that is larger than most previous studies, but comparable to recent findings by Sallenger and collaborators. While land subsidence increases SLR rates in the bay relative to global SLR, the acceleration results support Sallenger et al.'s proposition that an additional contribution to SLR from climatic changes in ocean circulation is affecting the region. Citation: Ezer, T., and W. B. Corlett (2012), Is sea level rise accelerating in the Chesapeake Bay? A demonstration of a novel new approach for analyzing sea level data, Geophys.

Over the past few decades the pace of relative sea level rise (SLR) in the Chesapeake Bay (CB) has been 2-3 times faster than that of the globally mean absolute sea level. Our study is part of ongoing research that tries to determine if this SLR trend is continuing at the same pace, slowing down (SLR deceleration) or speeding up (SLR acceleration). We introduce a new analysis method for sea level data that is based on Empirical Mode Decomposition (EMD) and Hilbert-Huang Transform (HHT); the analysis separates the SLR trend from other oscillating modes of different scales. Bootstrap calculations using thousands of iterations were used to test the robustness of the method and obtain confidence levels. The analysis shows that most sea level records in the CB have significant positive SLR acceleration, so the SLR rates today are about twice the SLR rates of 60 years ago. The acceleration rates of our calculations are larger than some past studies, but comparable to recent results [1] who show accelerated SLR "hotspots" in the coastal areas between Cape Hatteras and Cape Cod. The results have implications for projections of future SLR and the impact on flooding risks in the Hampton Roads area. The contributions to SLR from land subsidence and climate-related changes in ocean circulation need further research.

Observations of Newark Bay, a sub-estuary network characterized by multiple junctions, reveal that fronts are generated by tidal flow through transitions in channel geometry. All fronts substantially contribute to along-channel estuarine heterogeneity, and most are associated with both changes in channel geometry and tidal velocity phase-shifts. A lift-off front forms at the mouth of the sub-estuary during ebb tide in response to the abrupt seaward channel expansion. While forming, the front is enhanced by a tidal velocity phase-shift; flood tide persists in the main estuary until 90 minutes after the start of ebb tide in the sub-estuary. A second lift-off front forms during ebb tide at a channel-side-channel junction and is enhanced by a lateral baroclinic circulation induced by baroclinic and barotropic tidal velocity phaseshifts between the main channel and side channel. The lateral circulation also bifurcates the along-channel ebb flow at the surface, generating a surface front above the lift-off front. At the head of Newark Bay, a second surface front forms during ebb tide at the confluence of two tributary estuaries. This confluence front is rotated across the mouth of the primary fresh water source by high velocities from the adjacent tributary estuary and is maintained through much of ebb tide by lateral straining and mixing. Although the overall stratification of Newark Bay would categorize it as a partially-mixed estuary, the fronts divide the density structure of the sub-estuary into a series of nearly homogeneous segments---a characteristic that is more often associated with fjords.

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