Elena Perez

Elena Perez

PhD Student in MIT-WHOI Joint Program

Research

Marine Heatwaves in the Northwest Atlantic

The Northwest Atlantic, which has exhibited evidence of accelerated warming compared to the global ocean, also experienced several notable marine heatwaves (MHWs) over the last decade. We analyze spatiotemporal patterns of surface and subsurface temperature structure across the Northwest Atlantic continental shelf and slope to assess the influences of atmospheric and oceanic processes on ocean temperatures. Here we focus on MHWs from 2015/16 and examine their physical drivers using observational and reanalysis products. We find that a combination of jet stream latitudinal position and ocean advection, mainly due to warm core rings shed by the Gulf Stream, plays a role in MHW development. While both atmospheric and oceanic drivers can lead to MHWs they have different temperature signatures with each affecting the vertical structure differently and horizontal spatial patterns of a MHW. Northwest Atlantic MHWs have significant socio-economic impacts and affect commercially important species such as squid and lobster.

Variability of Gulf Stream Warm Core and Cold Core Rings

The Northwest Atlantic is a region of the ocean that has experienced many changes in recent years that impact the physical and biological oceanography near the U.S. east coast. The primary focus of this paper is the changing nature of the Gulf Stream’s rings. Gangopadhyay et al. 2019 found a significant regime shift in the number of WCR formations from a census of sea surface temperature-derived (SST) rings. We use a dataset of sea surface height-derived (SSH) eddies to determine if the same results can be obtained. Here we show that no regime shift is detected in the dataset of SSH-derived eddies and the two dataset only identify a fraction of the same features. These results point to the possible dynamics behind the regime shift. The dataset of SSH-derived eddies is limited to eddies on the order of 100 km and lifespans ≥ 4 weeks. As there is no regime shift found in the SSH-derived eddies this points to a regime shift in eddies that are smaller than O(100 km) and live < 4 weeks. This is corroborated by Gangopadhyay et al., 2020 that found there was a regime shift in shorter-lived rings, but the regime shift was invariant to the size of rings. Additionally, the finding that the SST-derived rings and SSH-derived eddies identify different features puts into question the validity of using SSH-derived eddies to study Gulf Stream rings. This project promotes progress in the study of Gulf Stream ring variability and the changing nature of the Northwest Atlantic.

Sea Level Variability along U.S. NE Coast and its relationship to the Shelf Break Jet

The relationship between coastal ocean currents on sea level variability remains limited, particularly regarding the shelfbreak jet, a equatorward flowing current from the subpolar North Atlantic along the North American shelf break to Cape Hatteras, which K.R. Thompson (1986) hypothesized exerts significant control over coastal sea level variability. Despite almost 40 years passing since this hypothesis, no one, to our knowledge, has examined the dynamics between the shelfbreak jet and coastal sea level variability on the U.S. northeast coast. In this study, we develop a simple model for an idealized shelf break jet and discover that coastal sea level is more sensitive to changes in the jet’s transport compared to changes in the overturning circulation’s transport (Little et al. 2019). By addressing this research gap, our project enhances our understanding of the factors influencing coastal sea level variability, considering that previous studies have shown that the Gulf Stream does not exert significant control over sea level variability north of Cape Hatteras. Our straightforward model establishes a foundation for future investigations that can predict future sea level variability, or even past climate. The next phase of this project involves validating the model’s predictions against observations. Should the model demonstrate reliable performance, we could use the model to explore past, current, and future sea level variability, which is of significant relevance to the densely populated U.S. northeast coast. Ultimately, this work expands our comprehension of the factors influencing coastal sea level variability and its implications for human populations.

Variability of the Gulf Stream stability and drivers of mean latitudinal shifts 75-70W

The Gulf Stream path changes its behavior downstream of Cape Hatteras, North Carolina, shifting shoreward and seaward coherently between 75°W and 70°W, followed by a contorted and variable path downstream (east) of 70°W. During the satellite era (1993–2023), the Gulf Stream path between 75°W and 70°W showed an increasing trend in its position, with increasing shoreward excursions. We find that this part of the Gulf Stream is strongly correlated at zero-lag with an anomalous wind stress curl (WSC) pattern over the New England Seamounts in the eastern Slope and Sargasso seas (r = 0.71). We propose that Sverdrup dynamics and Rossby wave propagation may explain this strong relationship, such that the anomalous negative WSC over the New England Seamounts (∼ 65°W) generates positive sea surface height anomalies that propagate westward via baroclinic Rossby waves. When these positive SSH anomalies reach the western Slope Sea, they increase the cross- stream gradient, which causes the steepest area of the SSH gradient to shift shoreward (northwards). Consequently, the Gulf Stream between 75°W and 70°W to shifts shoreward. Furthermore, we find that over the same period, the separated Gulf Stream (specifically downstream of 70°W) has shown variability in its path stability, with some periods displaying a more stable, straight jet and others an unstable, meandering stream. To quantify the overall meandering behavior of the Gulf Stream, we define the cumulative Gulf Stream path variance. We investigate whether the path variance is related to changes in Deep Western Boundary Current (DWBC) transport or Gulf Stream position, and find no significant, zero-lag correlations. However, we find that the Gulf Stream path variance lags DWBC transport by 2.6 years (r = 0.29; p < 0.05), and lags the mean Gulf Stream position between 75°W and 70°W by 5.9 years (r = −0.52; p < 0.05).

Characterization of the Slope Gyre and Slope Jet from satellite and in-situ sub-surface observations

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