Hurricane‐forced upwelling and chlorophyll a enhancement within cold‐core cyclones in the Gulf of Mexico

Abstract

Clear skies, subsequent to Hurricane Ivan's passage across the Gulf of Mexico in September 2004, provided a unique opportunity to investigate upper ocean responses to a major hurricane. Oceanic cyclonic circulation was rapidly intensified by the hurricane's wind field (59–62 m s−1), maximizing upwelling and surface cooling (3–7°C) in two large areas along Ivan's track. Upward isothermal displacements of 50–65 m, computed from wind stress and sea surface height changes, caused rapid ventilation of thermoclines and nutriclines, leading to phytoplankton blooms with peak concentrations 3–4 days later. Wind speed changes along Ivan's track demonstrated that the cool waters (20–26°C) provided immediate negative feedback to the hurricane's intensity. Although our study focused on a relatively small ocean area, it revealed that mesoscale cyclones, in addition to warm anticyclones, may play an important role in producing along‐track hurricane intensity changes.

Slow translation speed causes rapid collapse of northeast Pacific Hurricane Kenneth over cold core eddy

“…Hurricanes Opal (1995), Katrina (2005), and Rita (2005) are examples of Gulf of Mexico TCs that intensified rapidly over areas of thick upper ocean warm layers [Shay et al, 2000;Jaimes and Shay, 2009]. Walker et al [2005] demonstrated that the lowest sea surface temperatures (SSTs) (20-26°C) in Hurricane Ivan's cool wake occurred within two weak CCEs along its track. Ivan's wind speeds decreased rapidly in close proximity to these TC-intensified CCEs, demonstrating immediate negative feedback from cool waters.…”

“…Both anticyclonic warm core eddies (WCEs) and cyclonic cold core eddies (CCEs) can rapidly impact tropical cyclone (TC) intensity changes [e.g., Emanuel, 1999;Shay et al, 2000;Lin et al, 2005Lin et al, , 2009aWalker et al, 2005;Wu et al, 2007;Jaimes and Shay, 2009;Zheng et al, 2008Zheng et al, , 2010. Hurricanes Opal (1995), Katrina (2005), and Rita (2005) are examples of Gulf of Mexico TCs that intensified rapidly over areas of thick upper ocean warm layers [Shay et al, 2000;Jaimes and Shay, 2009].…”

“…Price [1981] demonstrated that the contribution of transient upwelling to SST cooling increases as U h decreases. To investigate the role of upwelling in this case, we computed isotherm upwelling (Δη) from the change in SSH anomaly (Δh) using the reduced gravity approximation Δη = Àg/g′ Δh [Shay et al, 2000;Walker et al, 2005]. Assuming the suggested g′ value 0.035 for this ocean [Shay and Brewster, 2010] and Δh = À17 cm (SSHA change from 16 to 21 September) we estimated an isotherm upwelling of 48 m. The simulated temperature profile revealed 20°C water at 48 m ( Figure S1) ) when TC Rita tracked over a CCE.…”

Eos, Transactions, American Geophysical Union Volume 86, Number 48, 29 November 2005

“…gov). Strong current jets have been reported previously in the aftermath of storm events at the Mississippi delta [Walker et al, 1996].…”

“…from page 499 east of the Mississippi delta. Walker et al [2005] showed that the hurricane wind field energized the cyclone, enhancing upwelling of its relatively shallow thermocline.…”