Physical controls on the seasonal migration of the North Pacific transition zone chlorophyll front

The large seasonal migration of the transition zone chlorophyll front (TZCF) is of interest because a number of marine fauna, both commercial and endangered, appear to track it. Herein we examine the physical dynamics driving this seasonal migration of the TZCF. Vertical processes, traditionally viewed as controlling the dynamical supply of nutrients to surface waters, prove insufficient to explain seasonal variations in nutrient supply to the transition zone. Instead, we find that the horizontal Ekman transport of nutrients from higher latitudes drives the TZCF's southward migration. The estimated horizontal transport of nitrate supports up to 40% of new primary productivity in the region annually and nearly all of new primary productivity in the winter. The significance of horizontal advection to the North Pacific transition zone supports revising the paradigm that nutrients are supplied to surface waters from below. © 2010 by the American Geophysical Union.

Interior pathways of the North Atlantic meridional overturning circulation.

To understand how our global climate will change in response to natural and anthropogenic forcing, it is essential to determine how quickly and by what pathways climate change signals are transported throughout the global ocean, a vast reservoir for heat and carbon dioxide. Labrador Sea Water (LSW), formed by open ocean convection in the subpolar North Atlantic, is a particularly sensitive indicator of climate change on interannual to decadal timescales. Hydrographic observations made anywhere along the western boundary of the North Atlantic reveal a core of LSW at intermediate depths advected southward within the Deep Western Boundary Current (DWBC). These observations have led to the widely held view that the DWBC is the dominant pathway for the export of LSW from its formation site in the northern North Atlantic towards the Equator. Here we show that most of the recently ventilated LSW entering the subtropics follows interior, not DWBC, pathways. The interior pathways are revealed by trajectories of subsurface RAFOS floats released during the period 2003-2005 that recorded once-daily temperature, pressure and acoustically determined position for two years, and by model-simulated 'e-floats' released in the subpolar DWBC. The evidence points to a few specific locations around the Grand Banks where LSW is most often injected into the interior. These results have implications for deep ocean ventilation and suggest that the interior subtropical gyre should not be ignored when considering the Atlantic meridional overturning circulation.

Past, present and future change in the Atlantic meridional overturning circulation

Observations and numerical modelling experiments provide evidence for links between variability in the Atlantic Meridional Overturning Circulation (AMOC) and global climate patterns. Reduction in the strength of the overturning circulation is thought to have played a key role in rapid climate change in the past and may have the potential to significantly influence climate change in the future, as noted in the last two IPCC assessment reports (2001, 2007). Both IPCC reports also highlighted the significant uncertainties that exist regarding the future behaviour of the AMOC under global warming. Model results suggest that changes in the AMOC can impact surface air temperature, precipitation patterns and sea level, particularly in areas bordering the North Atlantic, thus affecting human populations. Here current understanding of past, present and future change in the AMOC and the effects of such changes on climate are reviewed. The focus is on observations of the AMOC, how the AMOC influences climate and in what way the AMOC is likely to change over the next few decades and the 21st 34 century. The potential for decadal prediction of the AMOC is also discussed. Finally, the outstanding challenges and possible future directions for AMOC research are outlined.

The genomes of two key bumblebee species with primitive eusocial organization

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

University of Michigan Men's Basketball Team, 1977

Back Row: asst. coach Bill Frieder, coach John Orr, Mark Lozier, David Baxter, Rickey Green, David Stavale, Thomas Staton, William Lelich, asst. coach Jim Boyce, asst. coach Dan Fife

Front Row: mngr. Mitchell Kaufman, Len Lillard, Alan Hardy, Phil Hubbard, co-captain Steve Grote, co-captain John Robinson, Jake Whitten, Joel Thompson, Robert Jones. mngr. John Anderson

University of Michigan Men's Basketball Team, 1980

Back Row: asst. coach Bill Frieder, Keith Smith, Mike McGee, John Garris, coach John Orr, Joe James, Mark Bodnar, John Johnson, trainer Peter Loubert, asst. coach Tom Kempf, asst. coach Mike Boyd

Front Row: mngr. Edwin VanDeWege, Paul Heuerman, John Garris, co-captain Martin Bodnar, co-captain Mark Lozier, Thad Garner, Leo Brown, mngr, Greg Ruggles

University of Michigan Men's Basketball Team, 1977

Back Row: asst. coach Bill Frieder, coach John Orr, Mark Lozier, David Baxter, Rickey Green, David Stavale, Thomas Staton, William Lelich, asst. coach Jim Boyce, asst. coach Dan Fife

Front Row: mngr. Mitchell Kaufman, Len Lillard, Alan Hardy, co-captain Steve Grote, co-captain John Robinson, Joel Thompson, Robert Jones. mngr. John Anderson

University of Michigan Men's Basketball Team, 1978

Back Row: asst. coach Bill Frieder, coach John Orr, Joel Thompson, K. Michael Robinson, Len Lillard, co-captain Phil Hubbard, Tom Bergen, Paul Heuerman, Alan Hardy, asst. coach Jim Boyce, asst. coach Dan Fife

Front Row: Mngr. Mitchell Kaufman, Marty Bodnar, Mark Lozier, Cornel Williams, co-captain David Baxter, Mike McGee, John Johnson, Tom Staton, Mark Bodnar, ?, mngr. John Anderson

University of Michigan Men's Basketball Team, 1979

Back Row: trainer Dan Campbell, equip. mngr. Bob Hurst, asst. coach Mike Boyce, Martin Bodnar, Mark Lozier, coach John Orr, John Johnson, Mark Bodnar, Keith Smith, asst. coach Bill Frieder, ?

Front Row: mngr. Edwin VanDeWege, Mike McGee, Paul Heuerman, John Garris, co-captain Phil Hubbard, , Alan Hardy, Thad Garner, co-captain Tom Staton

University of Michigan Men's Basketball Team, 1978

Back Row: Joel Thompson, K. Michael Robinson, Len Lillard, co-captain Phil Hubbard, Tom Bergen, Paul Heuerman, Alan Hardy

Middle Row: asst. coach Bill Frieder, head coach Johnny Orr, Marty Bodnar, Joh Lozier, Mark Bodnar, asst. coach Jim Boyce, asst. coach Dan Fife

Front Row: Mngr. Mitchell Kaufman, Cornel Williams, Thomas Staton, co-captain David Baxter, Mike McGee, John Johnson, ?, mngr. John Anderson